USB charging is something most of us don’t spend much time thinking about. A phone needs power, so we plug it into a charger. The same is true for headphones, cameras, flashlights, GPS devices, watches and dozens of other small electronic devices we use every day. What makes this arrangement work so well isn’t necessarily USB. It’s the electrical outlet sitting a few feet away.

Take away that electrical outlet for five or six days and USB charging becomes a much more interesting problem. Battery capacity matters, charging efficiency matters and even the USB cable starts to matter. More importantly, every bit of stored electricity has a physical weight because the battery cells required to store that energy have to be carried with you.

One interesting way to look at this problem is the Pacific Crest Trail. The PCT is obviously an extreme example, but that’s what makes it useful for this discussion. This isn’t intended to be an article about how to hike the Pacific Crest Trail. Instead, we’re using the trail to look at what happens to USB charging when electricity is no longer conveniently available.

A 2,650-Mile USB Charging Problem

The Pacific Crest Trail runs from the Mexican border through California, Oregon and Washington before reaching the Canadian border. The Pacific Crest Trail Association commonly describes the PCT as a 2,650-mile trail, although its January 2026 GIS data puts the latest estimate at 2,655.84 miles. The exact distance changes slightly over time as portions of the trail are rebuilt or rerouted.

A typical thru-hiker attempting the entire trail might spend approximately five months completing the trip. During that time, nearly everything needed for daily life is being carried on the person’s back. That obviously includes food, water, shelter and clothing, but today it increasingly includes something hikers from previous generations didn’t have to think about nearly as much: electricity.

A modern hiker might carry a smartphone for maps, GPS, photography, notes and communication. A satellite communicator or beacon provides another method of communication in areas without cellular service. Add a rechargeable headlamp, GPS watch, camera or earbuds and it isn’t difficult to end up with several devices that periodically need USB power.

Cellular coverage also cannot be assumed. The Pacific Crest Trail Association cautions that cell phones often don’t work on the PCT and discusses satellite communication devices as another tool used in the backcountry. The electronics are useful, but every electronic device creates an additional requirement for power.

Electricity Has Weight

At home there is essentially no physical penalty for using more electricity. Charging your phone three times instead of twice doesn’t make the wall outlet any heavier. Portable power is different because additional capacity requires additional battery cells, electronics and enclosure material.

This is where the relationship between battery capacity and weight becomes important. A hiker may have several devices with very different power requirements, and each device contributes something to the overall energy budget.

Not every hiker carries all of these devices, and some people will carry considerably more. The specific equipment isn’t really the point. The common problem is that whatever energy those devices consume eventually has to be replaced.

The Real Problem Isn’t 2,650 Miles

Fortunately, nobody needs to carry enough battery capacity to operate electronics continuously for the entire 2,650-mile trail. Long-distance hiking is organized around resupply points. According to the Pacific Crest Trail Association, hikers can generally purchase food every four to ten days, although reaching those locations may require leaving the trail and traveling into town.

Those resupply stops also provide opportunities to recharge electronics and power banks. From an energy standpoint, this changes the problem quite a bit. Instead of asking how much electricity someone needs for five months, the more useful question is how much electricity must be carried between reasonable opportunities to recharge.

For this example, we’ll use seven days. It isn’t intended to represent every section of the PCT or every hiker, but seven days gives us a reasonable period for looking at portable battery requirements.

Building a Seven-Day USB Power Budget

For our example, we’ll use four common electronic devices: a smartphone, satellite communicator, GPS watch and rechargeable headlamp. These aren’t based on specific products because we’re more interested in the electrical requirements than recommending a particular piece of equipment.

A reasonable seven-day energy estimate could look something like this:

These numbers are deliberately estimates because actual consumption can vary considerably. A smartphone being used continuously for GPS navigation, photography and communication will consume much more energy than a phone spending most of the day in airplane mode. Likewise, a headlamp might see very little use during long summer days.

For our example, however, the four devices require approximately 56 watt-hours of usable energy over seven days. That gives us something useful to compare against the capacity of a portable power bank.

A 20,000 mAh Battery Isn’t Really the Number We Need

Portable power banks are normally marketed by milliamp-hours, so we’re accustomed to seeing capacities such as 5,000 mAh, 10,000 mAh, 20,000 mAh and 30,000 mAh. The larger number generally means more stored energy, but milliamp-hours by themselves aren’t ideal when comparing devices operating at different voltages.

For this type of calculation, watt-hours (Wh) are more useful. A power bank advertised as 20,000 mAh will typically contain lithium cells with a nominal voltage around 3.6 to 3.7 volts. Using 3.7 volts for a simplified calculation gives us:

On paper, 74 Wh appears to provide a comfortable margin over our estimated 56 Wh requirement. The problem is that the entire 74 Wh isn’t going to arrive at the batteries inside our electronic devices.

The battery’s internal voltage has to be converted to USB output voltage, and the electronics performing that conversion consume some energy. The USB cable introduces resistance, and the receiving device performs another conversion while charging its own battery. As we’ve shown in our simple test of how USB cables affect charging, the cable itself can have a measurable effect on how much power reaches the device.

Every one of these steps introduces some loss. If our hypothetical power system delivered around 80–85% of the stored energy as useful charging energy, a 74 Wh battery might provide approximately 59–63 Wh to the devices.

Now the 20,000 mAh power bank that initially appeared to provide plenty of extra capacity is much closer to the estimated seven-day requirement. This is also why comparing power banks strictly by the advertised mAh number doesn’t tell the entire story.

How Much Does Portable Electricity Weigh?

This is where the subject gets particularly interesting for something like the Pacific Crest Trail. Long-distance hikers pay close attention to equipment weight because an item isn’t lifted once and put back down. It gets carried mile after mile for days or months.

Portable battery capacity therefore has a physical cost. The following table gives some broad representative ranges for common USB charging options. These aren’t specifications for any particular product, but they provide a useful idea of how capacity and weight tend to scale.

A 10,000 mAh battery therefore isn’t just 10,000 mAh of capacity. Depending on the design, it might also represent half a pound of equipment being carried for hundreds or thousands of miles. Doubling battery capacity may solve an energy problem, but it can just as easily create a weight problem.

For this type of application, the best battery capacity isn’t necessarily the largest battery someone can afford or fit inside a backpack. The better target is enough capacity to reliably reach the next charging opportunity while maintaining whatever reserve is considered reasonable.

USB-C Has an Unexpected Advantage in the Backcountry

USB-C is normally discussed in terms of data speed, charging power and the convenience of having a reversible connector. For a situation like this, USB-C offers another advantage that isn’t discussed as often: standardization can reduce the amount of equipment someone needs to carry.

If five electronic devices require four different charging cables, all four cables may need to come along. If those same five devices can charge from USB-C, one primary cable and perhaps a lightweight backup could potentially replace several cables and adapters.

Saving a few ounces doesn’t seem particularly important when the cables are sitting in a desk drawer. When those same ounces are being carried for 2,650 miles, reducing unnecessary equipment starts to make more sense.

This is a practical benefit of USB standardization that extends beyond convenience. In applications where size and weight matter, using a common charging interface can reduce the physical infrastructure needed to support the electronics.

USB Power Delivery Matters When You Get Back to Civilization

USB Power Delivery might seem less important for wilderness travel because a USB-C PD power bank capable of accepting 30, 45 or 65 watts doesn’t provide much benefit while someone is standing on a mountain without access to electricity. The benefit appears when that person finally reaches a place where electrical power is available again.

A hiker arriving in town may need to recharge a smartphone, satellite communicator, watch and a nearly depleted power bank. At that point, charging speed becomes important because there may be a limited amount of time available before returning to the trail.

A large battery replenished through an older low-power USB connection could require many hours. A power bank capable of accepting substantially higher USB-C PD input can potentially reduce that charging window, assuming the wall charger and available power source support the required output.

So USB Power Delivery doesn’t necessarily solve the off-grid portion of the problem. Its value is that it can reduce the amount of time required to refill the energy reserve before going off-grid again.

Why Not Just Carry a Solar Panel?

Solar power seems like an obvious solution for someone who will be outside for several months. Rather than carrying all of the required electricity in batteries, a portable solar panel provides a way to generate additional energy along the way.

The problem is that the solar panel also has to be carried. Its rated output is generally based on favorable conditions, while actual output depends on sunlight intensity, panel orientation, temperature, shading and how long the panel can remain properly exposed to the sun. A panel hanging vertically from a moving backpack or sitting at an unfavorable angle isn’t necessarily producing anything close to its advertised rating.

The environment also changes dramatically along the PCT. Southern California provides very different solar conditions from the Sierra Nevada or the heavily forested areas of Oregon and Washington. A system that works very well in one section may be much less productive in another.

This turns solar into the same type of weight-versus-energy calculation as a power bank. If a solar setup weighs 12 ounces, the important question isn’t simply whether the panel can generate electricity. Of course it can. The useful question is whether it can generate enough electricity between resupply points to justify carrying those 12 ounces instead of using that same weight for additional battery capacity.

The answer will depend on the season, location, weather and how the equipment is used, which is why solar isn’t automatically better or worse. It’s simply another option with a different set of tradeoffs.

The Cheapest Component Can Become the Most Important

There is another part of an off-grid USB system that’s easy to overlook. Someone might be carrying hundreds or even thousands of dollars worth of electronic equipment, yet a relatively inexpensive USB cable can prevent some of that equipment from being charged.

Cables bend, connectors collect dirt, equipment gets wet and cables get crushed inside backpacks. USB-C connectors can collect lint, sand or other debris, and a cable can simply be lost somewhere along the way. None of these situations are particularly serious at home because another cable is probably sitting in a drawer.

Fifty miles from the nearest replacement, a failed cable becomes a much bigger problem.

This doesn’t mean carrying several backup cables for every connector because doing that defeats the purpose of reducing weight. It does show why simplifying the charging system has value. Fewer connector types means fewer different cables to carry and fewer inexpensive components capable of disabling an otherwise functional piece of equipment.

The USB System Has Its Own Weight

To put all of this into perspective, we can assemble a basic charging system and look at the total weight. Again, these numbers are examples rather than specific equipment recommendations.

That works out to a little over one pound of equipment primarily dedicated to storing and moving electricity, and it doesn’t include the smartphone, GPS watch, satellite communicator, camera or headlamp themselves.

A larger battery adds more weight. Adding solar adds weight. Carrying several incompatible charging cables adds more weight again. On the other hand, reducing battery capacity too aggressively creates the possibility of running out of power before reaching the next charging opportunity.

This is why maximum battery capacity isn’t necessarily the goal. The goal is having enough capacity for the expected energy requirement, along with a reasonable reserve, without carrying substantially more battery than necessary.

Off-Grid USB Is Really Energy Management

The Pacific Crest Trail is an extreme example, but the same basic calculations apply to many situations where electronics need to operate away from dependable electrical power. Camping, field research, photography, disaster preparedness, remote construction, boating and overlanding all involve some version of the same problem.

At home, USB charging is mostly about convenience. Away from the electrical grid, it becomes a small energy system. There is a certain amount of stored energy, a certain amount of daily consumption and unavoidable losses as power moves between batteries, voltage converters, cables and devices. Charging rates determine how quickly that stored energy can be replaced, while the connectors and cables determine which devices can actually use it.

Then there is the physical side of the equation. Every battery, charger, cable and adapter takes up space and adds weight. The challenge is balancing those items against the amount of energy that will realistically be needed before another power source becomes available.

The PCT makes this relationship unusually easy to see. A 20,000 mAh power bank sitting in a desk drawer doesn’t seem particularly heavy. Carry the same battery from Mexico to Canada and the extra weight becomes much more noticeable.

Most of us don’t need to think about USB this way because there is usually another electrical outlet nearby. Remove the outlet for a week and the relationship between battery capacity, charging efficiency, cable quality, charging speed and weight becomes much easier to understand.

This article originally appeared on GetUSB.info. Subscribe to GetUSB updates.

Disk image files can be confusing because two files may appear to accomplish the same thing while actually being designed for very different purposes. A good example is the difference between a VHD file and an IMG file.

Both formats can contain partitions, file systems, boot information and files. Both can represent what appears to be a complete storage device. However, when the objective is duplicating physical USB flash drivesThe process of copying data from one USB flash drive to multiple USB drives simultaneously or sequentially., SD cards or other flash memory devices, the distinction between these formats becomes important.

The simplest way to explain the difference is this:

An IMG file represents the sectors of a disk. A VHD file represents a virtual disk inside a container.

For physical media duplication, that distinction is the primary reason an IMG file is the preferred format.

What Is an IMG File?

An IMG file is generally a raw representation of a storage device. Think of the storage device as a long sequence of sectors identified by Logical Block AddressesLogical Block Addresses (LBAs) are numerical identifiers for sectors on a storage device used to locate data., or LBAs.

Physical USB Drive

LBA 0
LBA 1
LBA 2
LBA 3
...
Last LBA

       |
       v

IMG File

LBA 0
LBA 1
LBA 2
LBA 3
...
Last LBA

If the physical device uses 512-byte logical sectors, the IMG file can represent those sectors sequentially from the beginning of the device through the end of the captured image.

This means an IMG file can preserve much more than the files visible in Windows File Explorer. Depending on how the image was created, it can include the MBR or GPT partition structure, boot sectors, partition information, file systems, hidden partitions and other sector-level information.

This direct relationship between the image and physical storage media is exactly what makes the IMG format useful for USB duplication.

What Is a VHD File?

VHD stands for Virtual Hard Disk. As the name suggests, the format was created to represent a hard disk in a virtual computing environment.

A VHD can contain partitions, file systems and files just like a physical disk. An operating system can mount the VHD and interact with it much like another storage device.

The important difference is that the VHD file itself is a container. Information exists within the file that describes and manages the virtual disk.

IMG

[ Raw Disk Sectors ]


VHD

[ Virtual Disk Data ][ VHD Metadata ]

There are also different types of VHD files. A fixed VHD allocates storage for the entire virtual disk, while a dynamic VHD can grow as information is added. Differencing VHD files can reference another virtual disk and store only changes made relative to that parent disk.

These are useful features in virtualization. They are not particularly useful when the objective is making an exact physical USB storage device.

Why the Difference Matters for USB Duplication

A USB duplicationThe process of copying data from one USB flash drive to multiple USB drives simultaneously or sequentially. system ultimately needs to write information to a physical block storage device. At some point, data must become sectors written to the target media.

With a raw IMG file, that relationship is straightforward:

IMG LBA 0     -> USB LBA 0
IMG LBA 1     -> USB LBA 1
IMG LBA 2     -> USB LBA 2
IMG LBA 3     -> USB LBA 3
...
IMG Last LBA  -> USB Last LBA

This is a natural fit for physical media duplication because the image is already expressed in the same basic structure used by the target storage device.

A VHD introduces another layer.

Virtual Disk
     |
     v
VHD Container
     |
     v
Interpret VHD Structure
     |
     v
Reconstruct Disk Data
     |
     v
Physical USB Media

Before the information can be treated as a raw physical disk image, software must understand the VHD format, determine the type of VHD being used and correctly reconstruct the virtual disk represented inside the container.

For USB duplication, this extra layer provides little benefit. It simply introduces another format that must be interpreted before the information can be written to physical media.

Can You Rename a VHD File to IMG?

No. Changing the file extension does not change the structure of the file.

For example, renaming:

master.vhd

to:

master.img

does not convert the VHD into a raw disk image. It only changes the filename.

The internal VHD structure and metadata remain exactly the same.

This distinction is important because imaging or duplication software expecting raw sector data may interpret those additional structures as part of the physical disk image. A VHD should therefore be properly converted or exported to a raw image format rather than simply renamed.

IMG Makes Disk Capacity Easier to Understand

Another advantage of raw images becomes apparent when dealing with storage capacity.

USB flash drives marketed with the same capacity do not necessarily contain exactly the same number of sectors. Two devices labeled as 64GB, for example, can have slightly different LBA counts depending on the controller, NAND configuration and manufacturing process.

With a raw IMG file, the relationship between sector size, LBA count and image size is predictable.

For a device using 512-byte logical sectors:

Image Size = LBA Count x 512 bytes

This becomes especially important when duplicating an image onto replacement media. If the source image requires more LBAs than exist on the target device, the target is physically too small to contain the complete image even if both products are marketed with the same nominal capacity.

There is another detail worth understanding here: the physical capacity of the device and the size of the partition stored inside an image are not necessarily the same thing. We explain that distinction in more detail in why the partition size matters inside an image file.

Using a raw image makes these relationships easier to identify because there is no virtual disk container sitting between the image file and the physical storage device.

VHD Is Not a Bad Format – It Was Designed for a Different Job

None of this means VHD is an inferior disk imageA disk image is a file that contains a complete copy of the data and structure of a storage device, including partitions, file systems, and boot information. format. It simply solves a different problem.

VHD is useful when working with virtual machines, virtual storage, software development environments, operating system testing and situations where a disk needs to exist as a manageable virtual device.

IMG is better suited to situations where the final destination is physical storage media. Even Windows can sometimes create confusion when working with raw image files because an IMG file is not necessarily handled the same way as a virtual disk container. If that becomes an issue, we have a separate article covering a solution for mounting an IMG file in Windows.

The Short Answer: Use IMG for USB Duplication

If the end product is a physical USB flash drive, SD card, microSD card or similar block storage device, a raw IMG file provides the most direct representation of the information that needs to be written to the media.

VHD adds a virtualization container that provides useful features when working with virtual machines, but those features provide little value during physical media duplication.

There are certainly software tools capable of reading VHD files and converting the virtual disk into another format. However, that conversion step reinforces the underlying point: before the virtual disk can be treated like a raw physical disk image, the VHD container must first be interpreted.

With IMG, that extra translation layer is unnecessary.

For physical USB, SD and microSD duplication, keep the master image simple. Use a raw IMG file.

VHD vs IMG, USB Duplication, Disk Image File, USB Flash Drive Imaging, Raw Disk Image

Learn the difference between VHD and IMG files, why the formats matter, and why raw IMG files are preferred for USB, SD and microSD duplication.

This article originally appeared on GetUSB.info. Subscribe to GetUSB updates.

A company purchases 10,000 USB flash drives for a product with a five-year manufacturing life cycle. The drives are placed into inventory, and some of those drives might not be used for three, four or even five years. When somebody finally opens that last carton and plugs one of those USB drives into a computer, will it still work?

That is a surprisingly difficult question to answer with a Google search.

There is plenty of information about how long a USB flash drive lasts while being used. Most discussions focus on NAND write endurance, program/erase cycles, connector cycles or how long data remains stored in NAND memory. We have discussed many of those factors in our article about the lifespan of a USB flash drive.

But that isn’t the question being asked here.

This article is about new USB flash drives sitting in inventory before they are ever put into service. This is an important distinction for medical device companies, industrial manufacturers, equipment manufacturers and other organizations purchasing components against a bill of materials (BOM) that might remain active for several years.

So How Long Can an Unused USB Flash Drive Sit in Storage?

There isn’t a single expiration date that applies to every USB flash drive, but as a practical inventory guideline, new USB flash drives stored under reasonable warehouse conditions should remain usable for several years.

For business planning purposes, we would consider one to five years of storage a reasonable inventory window. Storage beyond five years does not mean the drives suddenly become unreliable, but at that point periodic validation becomes increasingly important.

These time periods are not manufacturer warranties or guaranteed retention specifications. They are practical inventory-planning guidelines. Actual results depend on the NAND flash technologyA type of non-volatile storage technology designed to store large amounts of data efficiently and retrieve it when needed., controllerA hardware component that manages data flow between a USB drive and its memory chips., PCB construction, packaging, temperature, humidity and storage environment.

A USB Drive Sitting on a Shelf Is Not Wearing Out

One reason this topic gets confusing is because USB flash drive life expectancy is normally discussed in terms of usage.

NAND flash memory has a finite number of program and erase cycles. USB connectors also have a finite number of insertion cycles. Controllers generate heat while operating, and electronic components experience electrical and thermal stress while being used.

None of those things are happening to a USB flash drive sitting inside a sealed carton.

A new USB flash drive does not accumulate program/erase cycles while sitting in inventory. The USB connector isn’t being inserted and removed. The controller isn’t continuously operating. The NAND isn’t being repeatedly written and erased.

In simple terms, a blank USB flash drive does not wear out simply because it is sitting on a warehouse shelf.

Time still matters, but now the primary concerns become the storage environment and the natural aging of electronic components rather than normal operational wear.

Blank Inventory and Data Retention Are Different Questions

There is another important distinction to make.

When somebody asks whether a USB flash drive will retain files for ten years, they are asking about data retention. NAND flash stores information as electrical charge inside memory cells, and over long periods that charge can gradually change. Temperature, NAND wear and the type of flash memory all influence retention.

But a company storing unused USB inventory is asking a different question:

Will the device itself still function when we eventually put it into service?

Data retentionThe length of time data remains stored and accessible on a storage device without degradation. is generally a much smaller concern for unused inventory than it is for a flash drive holding irreplaceable user data. However, it would not be technically correct to say an unused USB flash drive contains no important stored information.

The controller contains firmware and configuration information required to operate the device. Depending on the controller architecture, some flash-management information may also reside in NAND memory.

So even an unused USB drive is still an electronic storage device. The difference is that it has not experienced years of user writes, erase cycles and normal operating wear.

Why Companies Might Intentionally Buy Several Years of USB Inventory

At first glance, purchasing three or five years of USB flash drive inventory might sound excessive. For some manufacturers, however, it can make a lot of sense.

Consider a medical device manufacturer that qualifies a particular USB controller, NAND configuration and firmware combination for use with its product. Or consider an industrial equipment manufacturer shipping firmware updates, configuration software, service utilities or documentation on USB media.

Once a specific component configuration has been tested and approved, purchasing doesn’t necessarily want a completely different USB flash drive six months later.

A component change can trigger compatibility testing, engineering review, documentation changes, purchasing approval and potentially additional validation work. In regulated industries, seemingly small component changes can create a much larger internal process than the cost of the component itself would suggest.

This is where BOM planning becomes important.

If a product is expected to remain in production for three or five years, purchasing enough inventory to support a significant portion of that manufacturing cycle can reduce supply-chain uncertainty and help maintain a consistent hardware configuration.

Memory Pricing Adds Another Reason to Consider Long-Term Inventory

Flash memory pricing is cyclical. NAND prices can fall dramatically when the market is oversupplied and increase when production is constrained or demand increases.

That makes purchasing decisions more complicated.

Imagine a manufacturer expects to consume 25,000 identical USB flash drives during the next three years. Buying those drives in smaller quantities every few months exposes the company to changing NAND prices, controller availability and possible component substitutions.

If memory pricing is rising, purchasing a larger quantity today can potentially lock in both pricing and component availability.

But that purchasing decision immediately creates another engineering question:

If we buy three years of USB inventory today, can those drives safely sit in our warehouse until we need them?

In most reasonable storage environments, that is a manageable problem. The key is understanding how the inventory is stored and having a simple validation plan.

Warehouse Conditions Matter More Than the Calendar

There is a major difference between storing USB drives for five years in a climate-controlled electronics warehouse and storing the same drives for five years in a building experiencing extreme temperature and humidity swings.

Consider an uncontrolled warehouse in Illinois. During the year, inventory could experience hot summer temperatures, very cold winter temperatures and significant changes in humidity.

The USB drives may tolerate those conditions perfectly well, but environmental cycling introduces additional concerns that wouldn’t exist in a stable indoor environment.

Temperature is one consideration. Sustained high temperatures are generally more concerning for long-term electronic storage than ordinary cool conditions.

Humidity is another. Moisture can contribute to corrosion of exposed metal contacts, PCB components and connectors.

Temperature cycling also matters. Moving very cold inventory into a warm and humid environment can create condensation. The same principle applies to many electronic products, not just USB flash drives.

Airborne contaminants can also become a factor in industrial environments. Dust, chemicals, salt and other contaminants can attack exposed electrical contacts over long periods.

For these reasons, USB drives intended for long-term inventory should remain in their original sealed packaging whenever possible. Additional moisture-resistant packaging and desiccant can also be considered when the storage environment is known to have high humidity.

Don’t Buy Five Years of Inventory and Forget About It for Five Years

If a company purchases a large quantity of USB flash drives intended to support several years of manufacturing, there is a very simple way to reduce the risk: test samples periodically.

This doesn’t mean opening and testing thousands of drives every year. A company can retain a small sample from the original production lot and establish an inventory validation schedule.

The exact sample size and testing requirements will depend on the organization and application. A promotional USB drive doesn’t require the same validation process as removable media included with industrial or medical equipment.

At minimum, testing should confirm that the device enumerates correctly, reports the expected capacity and can successfully write and read across the storage area being tested.

For more critical applications, companies may also want to compare sustained write/read performance against the original production-lot baseline.

Should Old USB Inventory Be Powered Up Just to Refresh It?

For normal commercial inventory, we would not recommend periodically plugging in every USB drive simply because it has been sitting in storage.

Doing that creates additional handling, opens packaging and introduces connector cycles without necessarily providing a meaningful benefit.

A better approach is statistical sampling. Keep the bulk inventory sealed and periodically test representative units from the same production lot.

If those samples begin showing unexpected behavior, then the company has a reason to expand testing before releasing additional inventory into production.

What About USB Drives That Already Contain Data?

This changes the discussion considerably.

If USB drives were programmed before being placed into long-term storage, then the company is no longer concerned only about whether the hardware will function. Data retention also becomes part of the storage strategy.

For example, a manufacturer might pre-load firmware, software, documentation or recovery images onto thousands of drives and then warehouse those drives for several years.

That scenario deserves more conservative validation because the requirement is now twofold: the USB device must operate and the previously programmed data must remain correct.

Periodic sample verification becomes even more important in this situation, particularly when the media contains information required for installation, recovery or equipment operation.

Long-Term USB Inventory Can Be a Reasonable Business Decision

There is nothing inherently wrong with purchasing several years of USB flash drive inventory.

For companies managing long-life products, stable BOMs or qualified component configurations, purchasing inventory in advance can actually reduce risk. It can protect against component substitutions, supply shortages and unfavorable changes in NAND pricing.

The mistake is assuming that because USB flash drives are small and inexpensive they don’t deserve an inventory strategy.

Keep long-term inventory properly packaged. Avoid unnecessarily harsh temperature and humidity conditions. Maintain production-lot records. Retain samples. Test those samples periodically.

A USB flash drive sitting unused for three or five years isn’t automatically an old or worn-out flash drive. In many cases, it has experienced virtually none of the operational stresses associated with flash drive wear.

And that brings us to the practical conclusion:

Buying several years of USB flash drive inventory isn’t inherently a bad idea. Buying several years of inventory without a storage and validation plan is.

This article originally appeared on GetUSB.info. Subscribe to GetUSB updates.

When working with USB flash drives, SD cards, microSD cards, SSDs, and other block storage devices, two numbers are particularly useful: the sector size and the LBA count. Together, these values describe the addressable capacity of a storage device at the block level.

LBA stands for Logical Block Addressing. Rather than describing a storage device using older physical concepts such as cylinders, heads, and sectors, modern storage devices are addressed as a sequential collection of logical blocks. Each block is assigned a number, starting with LBA 0 and continuing through the last available logical block on the device.

In simple terms, the LBA countThe total number of addressable logical blocks (sectors) on a storage device. tells us how many addressable sectors are available, while the sector size tells us how many bytes are contained in each of those sectors.

Why Exact LBA Count Matters

For normal file storage, a small difference in raw device capacity usually goes unnoticed. A user copying documents or photographs onto a flash drive generally does not care whether two nominally identical drives contain slightly different numbers of sectors.

Disk imaging and duplication are different.

A source device may contain a partition or disk structure extending very close to its final available LBA. If the target device contains fewer LBAs than the source, even by a relatively small amount, a sector-for-sector image may not fit.

This can happen even when both devices are marketed with exactly the same capacity. Two devices labeled 32GB, 64GB, or 128GB are not necessarily guaranteed to contain the exact same number of addressable logical sectors.

The issue becomes particularly important with structures located near the end of a disk. GPT-formatted media, for example, maintains a backup GPT header near the end of the device. Changing the available LBA range can therefore affect more than simply the amount of unused space at the end of a disk.

LBA Is More Precise Than the Capacity Printed on the Device

Commercial capacity labels such as 32GB, 64GB, and 128GB are useful for consumers, but they are not precise descriptions of storage geometry.

When exact compatibility matters, three values provide a much clearer picture:

Knowing these values makes it possible to determine exactly how much addressable storage exists and whether one storage device is truly large enough to contain the complete block structure of another.

The Relationship Between LBA and Sector Size

The basic capacity calculation is:

For a device using 512-byte logical sectors:

The calculation can also be reversed. If the total device capacity in bytes and logical sector size are known, the LBA count can be calculated as:

For example, consider a device with an LBA count of 60,125,184 and a logical sector size of 512 bytes:

This relationship becomes especially important when comparing storage devices for disk imaging, duplication, cloning, forensic work, or other applications where the exact number of available sectors matters.

Why 512-Byte Sectors Are So Common

A logical sector size of 512 bytesThe logical block size of 512 bytes commonly used in storage devices for addressing data. has been the traditional standard for storage devices for decades. It remains extremely common for USB flash drives, memory cards, and many other storage devices because of compatibility with operating systems, file systems, boot structures, controllers, and existing software.

For this reason, when examining a typical USB flash drive, a 512-byte logical sector size is generally a reasonable expectation. However, it should not simply be assumed when exact capacity matters. Windows can report the logical sector size directly, and checking the actual value removes any uncertainty.

Some modern storage devices use 4,096-byte physical sectors while continuing to present 512-byte logical sectors to the operating system. This configuration is commonly referred to as 512e, or 512-byte emulation. Other devices can expose 4,096-byte logical sectors directly, commonly called 4Kn.

Why Would a Device Use a Different Sector Size?

Larger sectors can improve storage efficiency because fewer sectors are required to describe the same amount of capacity. A 4,096-byte sector contains eight times as much data as a 512-byte sector. Larger sectors can also reduce some addressing and error-correction overhead and better match the internal architecture of modern high-capacity storage devices.

However, changing the logical sector size has compatibility implications. Operating systems, boot loaders, file systems, duplication equipment, embedded systems, and specialized software may expect 512-byte logical sectors. This is one reason a storage device may internally use 4K physical sectors while still presenting 512-byte logical sectors to the host.

How Sector Size Changes the LBA Count

The same byte capacity can have very different LBA counts depending on the logical sector size.

Consider a hypothetical storage area containing 4,096,000 bytes.

The amount of storage has not changed. Only the size of each addressable logical block has changed. The 4K-sector device therefore requires one-eighth as many LBAs to describe the same byte capacity.

This is why an LBA count by itself does not completely describe storage capacity. The logical sector size must also be known.

Converting LBA to MB and MiB

When converting an LBA count into a more familiar capacity value, it is important to distinguish between decimal megabytes (MB) and binary mebibytes (MiB). Although the terms are often used interchangeably in casual discussion, they represent different numbers of bytes.

This distinction explains why storage capacities can appear different depending on how a utility or operating system reports the value. Drive manufacturers commonly advertise capacity using decimal units, while many operating-system and technical calculations have traditionally used binary units.

For a device using 512-byte logical sectors, converting an LBA count to MiB is particularly easy:

This is a useful shortcut when working with USB flash drives that report 512-byte logical sectors.

The reverse calculation is:

For example, adding 7 MiB of addressable capacity to a 512-byte-sector device requires:

This means a device with 60,110,848 LBAs would need an additional 14,336 logical sectors to reach 60,125,184 LBAs. With 512-byte logical sectors, that difference represents exactly 7 MiB of addressable capacity.

If decimal MB is required instead, the calculation uses 1,000,000 bytes per MB rather than 1,048,576 bytes per MiB:

How To: Check Sector Size in Windows PowerShell

Windows PowerShell makes it easy to examine the logical and physical sector sizes reported by attached storage devices.

Open PowerShell and enter: (copy and paste)

Get-Disk | Select-Object Number, FriendlyName, BusType, LogicalSectorSize, PhysicalSectorSize

This command lists the disks recognized by Windows and displays the disk number, device name, bus type, logical sector size, and physical sector size.

The output might show a USB device similar to this:

Number  FriendlyName       BusType  LogicalSectorSize  PhysicalSectorSize
2       USB Flash Drive    USB      512                512

The important value for calculating the LBA count is LogicalSectorSize. In this example, each logical block presented to Windows contains 512 bytes.

It is important to distinguish the logical sector size from the physical sector sizeThe logical block size of 512 bytes commonly used in storage devices for addressing data.. LBA addresses the logical blocks presented to the operating system. Therefore, when calculating an LBA count, the LogicalSectorSize value is the relevant number.

For example, a 512e drive may report a logical sector size of 512 bytes and a physical sector size of 4,096 bytes. Windows still addresses that device using its 512-byte logical blocks, so the LBA calculation is based on 512 bytes rather than the underlying 4,096-byte physical sectors.

How To: Get the LBA Count with PowerShell

Once the correct disk number has been identified, PowerShell can calculate the total LBA count directly.

For example, if the USB device is Disk 2:(copy and paste)

Get-Disk -Number 2 | Select Number, FriendlyName, LogicalSectorSize, @{Name="LBA_Count";Expression={$_.Size / $_.LogicalSectorSize}}

The calculation being performed by PowerShell is simply:

The PowerShell command does not assume that every storage device uses 512-byte logical sectors. Instead, it reads the LogicalSectorSize reported by the selected device and uses that value in the calculation.

This means the same command works with traditional 512-byte logical sector devices, 512e drives, and native 4Kn drives. For a 512-byte or 512e device reporting 512-byte logical sectors, the device size is divided by 512. For a native 4Kn device reporting 4,096-byte logical sectors, the device size is divided by 4,096.

This distinction is important because a 512e drive may physically store data in 4,096-byte sectors while still presenting 512-byte logical sectors to Windows. LBA numbering follows the logical block size exposed to the operating system, not necessarily the physical sector size used internally by the storage device.

The Simple LBA Formulas

For quick reference, these are the core calculations used when working with LBA values:

That last equation is particularly useful when determining exactly how much smaller one USB flash drive is compared with another. The important detail is that dividing the LBA difference by 2,048 produces a result in MiB, not decimal MB, when the devices use 512-byte logical sectors.

This article originally appeared on GetUSB.info. Subscribe to GetUSB updates.

I recently read an article arguing that smart TVs are being held back because manufacturers continue to use USB 2.0 ports instead of USB 3.0. The argument sounds reasonable at first. USB 3.0 is newer, USB 3.0 is faster, therefore a modern television should have USB 3.0.

But the more I thought about it, the less the argument made sense.

There are several reasons why USB 2.0 remains perfectly reasonable for a television, and the biggest one is simple: a television isn’t a computer. The USB port on the back of a TV has a very specific job, and adding substantially more bandwidth to that port doesn’t necessarily make the television perform any better.

USB 2.0 Already Has Enough Bandwidth for 4K Video

The first issue is bandwidth.

USB 2.0 has a theoretical maximum transfer rate of 480 MbpsThe theoretical maximum data transfer rate of USB 2.0, equal to 480 megabits per second.. Nobody should expect to get the full 480 Mbps of actual file-transfer performance from a USB 2.0 flash drive. Protocol overhead, the USB controller, the flash memory and the storage device itself all reduce real-world performance.

However, even if we use a much more realistic USB 2.0 read speed of approximately 25 to 40 MB/s, we’re still talking about roughly 200 to 320 Mbps of available data throughput.

Now compare that with the amount of data a television actually needs to play compressed 4K video.

A typical compressed 4K video stream may require somewhere around 20 to 60 Mbps. Even a very high-quality HEVC video running at 100 Mbps requires only about 12.5 MB/s of sustained read performance.

USB 2.0 can handle that.

Movie File Size Isn’t the Important Number

This is also where the argument about “large 4K movie files” becomes misleading. The physical size of the movie file doesn’t determine how quickly the USB interface needs to read it. The bitrate does.

A 20GB movie encoded at 60 Mbps and a 100GB movie encoded at 60 Mbps place essentially the same bandwidth requirement on the USB connection during playback. The larger file contains more data, but the television still only needs to consume that data at approximately 60 Mbps while the video is playing.

This is very different from the way most of us think about USB performance on a computer.

If I’m copying 100GB of data from one USB device to another, I absolutely care whether I’m using USB 2.0 or USB 3.0. I don’t want to sit there waiting for 100GB to transfer at USB 2.0 speeds. In that application, USB 3.0 provides an obvious and significant benefit.

A television isn’t doing that.

For normal media playback, the television is primarily reading a continuous stream of data from the USB storage device and feeding that data into the video decoder. Once the USB interface can supply data faster than the decoder consumes it, making the USB connection ten times faster doesn’t make the movie play ten times better.

The pixels don’t get sharper because they arrived early.

A Smart TV USB Port Isn’t a PC USB Port

There is another reason television manufacturers may not be rushing to install faster USB ports, and I think this one gets overlooked even more often.

The USB port on a smart TV is deliberately limited by the television manufacturer.

Plugging a USB device into a Windows PC gives you access to an operating system designed to support thousands of USB devices, drivers and USB device classes. A smart television is completely different. As we’ve explained before about why USB works differently on smart TVs, the manufacturer controls which USB functions the television recognizes and what those devices are allowed to do.

A television might support USB mass storage for movies, photos and music. It might support a keyboard or certain approved accessories. Some televisions use USB for firmware updates or service functions. Other models and regions may support recording television programs to attached USB storage.

Those capabilities are controlled by the television’s firmware and operating system. They aren’t determined by whether the physical USB connection happens to operate at USB 2.0 or USB 3.0 speeds.

There are also good security reasons for manufacturers to keep that USB environment tightly controlled. Every additional USB device class, driver and external interface creates more software to maintain, more compatibility scenarios to test and potentially another attack surface.

Remember, a smart TV isn’t necessarily an isolated appliance anymore. It may be connected to the home’s Wi-Fi network alongside computers, phones, security cameras, network storage and other smart devices. If a malicious USB device or compromised flash drive were able to exploit a vulnerability in the television’s USB stack, media parser or firmware, the problem could potentially extend beyond simply crashing the television. A compromised network-connected device could become another foothold inside the home network.

This gives television manufacturers another reason to be conservative about what the USB port is allowed to recognize and execute. Supporting basic mass storage for movies, photos and music is one thing. Supporting a broad collection of USB peripherals, drivers and device classes is something entirely different. From the manufacturer’s perspective, there is very little reason to turn the USB port into a general-purpose computer interface when the television doesn’t need one.

Putting a 5 Gbps USB 3.0 controller into a television doesn’t magically turn the USB port into the USB port on your computer.

Would USB 3.0 Provide Any Benefit?

There are certainly situations where USB 3.0 could be useful on a television. Faster storage could improve operations involving large amounts of data. USB 3.0 can also provide additional power compared with a standard USB 2.0 port. A manufacturer could design a television to support higher-speed USB Ethernet adapters or other peripherals where the additional bandwidth would actually be useful.

Those are legitimate advantages.

But that is very different from saying USB 2.0 is preventing modern televisions from properly playing 4K videoA high-resolution video format with approximately 4,000 pixels across the horizontal axis..

For ordinary compressed video playback, USB 2.0 already provides considerably more bandwidth than the television normally requires. If a 4K movie is stuttering when played from a USB storage device, I would look at the storage device’s sustained read performance, video bitrate, codec, container format, filesystem, television decoder and firmware before automatically blaming the USB 2.0 interface.

Sometimes Faster Doesn’t Solve the Problem

Sometimes an older interface remains in a product because the manufacturer is saving a few dollars. I’m sure that happens.

Sometimes, however, an older interface remains because the faster interface doesn’t solve a meaningful problem.

For playing compressed video from USB storage on a smart TV, USB 2.0 is a good example. USB 3.0 is unquestionably faster.

The television just doesn’t need most of that speed.

This article originally appeared on GetUSB.info. Subscribe to GetUSB updates.

GetUSB isn’t becoming an artificial intelligence website. There are already plenty of those, and most days the world probably doesn’t need another article explaining that AI is going to change everything.

What has caught our attention is something a little more practical.

The deeper you get into how artificial intelligence actually works, the more the conversation starts sounding familiar. Memory bandwidth matters. Storage matters. NAND flash matters. DRAM matters. PCIe matters. Moving enormous amounts of data from one place to another matters. These are subjects we’ve been following for years, long before every product announcement needed the letters “AI” somewhere in the first paragraph.

Over the past several months we’ve written a number of articles looking at AI from that hardware perspective. Rather than chasing every new model or software announcement, we’ve been interested in what has to happen underneath all of it.

Looking back, eight articles in particular fit together surprisingly well.

Portable AI Accelerators vs Cloud AI: What Small Businesses Should Actually Pick?

One of the more interesting changes in AI is that running an AI workload doesn’t automatically mean sending everything to a massive data center. Smaller AI accelerators are making local inference practical for applications that don’t require the horsepower of a giant cloud-based model.

In our article about portable AI accelerators versus cloud AI, we looked at the tradeoffs between the two approaches. Cloud AI provides enormous computing resources, but local AI brings some interesting advantages of its own, including privacy, predictable operating costs, lower latency and the ability to continue working without an internet connection.

The important point isn’t that one approach wins. It is that AI processing is starting to spread out. Some jobs belong in the cloud. Some make considerably more sense sitting on a local computer or edge device.

Inside an AI Computer: Why Modern AI Systems Consume So Much Memory

A GPU gets most of the glory in an AI computer, but a powerful processor isn’t particularly useful if it spends its time waiting for data.

That led us to look inside an AI computer and explain why modern AI systems consume so much memory. AI models contain huge numbers of parameters, and those parameters have to be stored, loaded and moved through the system while calculations are taking place.

This is one of the recurring themes behind AI hardware. Computing power has increased dramatically, but feeding that computing power has become a problem of its own. The processor might be capable of doing the work, but only if the rest of the system can keep up.

NAND Isn’t Going Away, But AI Servers Now Depend on More Than Flash

Given our background, NAND flash was an obvious place for us to start digging.

AI isn’t making NAND obsolete. Quite the opposite. Models, training data, databases and generated information all need persistent storage, and flash remains extremely important. But AI servers now depend on much more than NAND flash because storage capacity is only one part of the problem.

An SSD can hold a tremendous amount of information, but the processor can’t perform calculations directly against everything sitting on an SSD at full speed. Data has to move through different levels of the memory hierarchy, each with its own balance of capacity, speed and cost.

AI has made that hierarchy much more visible.

What Is High Bandwidth Memory and Why Does AI Depend on It?

High Bandwidth Memory, usually shortened to HBM, went from being a fairly specialized memory technology to something regularly mentioned in discussions about AI hardware.

There’s a good reason.

In our explanation of what High Bandwidth Memory is and why AI depends on it, we looked at the problem HBM is designed to solve. Modern GPUs can perform an extraordinary number of calculations, but conventional memory architectures can become a bottleneck when those processors need enormous amounts of data delivered continuously.

HBM puts extremely fast memory very close to the processor and provides much greater memory bandwidth than conventional memory arrangements. It is expensive and complicated, but when you’re trying to keep an AI accelerator fed with data, bandwidth can be just as important as raw processing speed.

Think of it as owning a very fast factory. Making the machines inside the factory faster doesn’t accomplish much if the loading dock can’t deliver raw material quickly enough.

Why DRAM Alone Can’t Keep Up With AI Anymore

DRAM isn’t disappearing either. There is simply too much data.

We explored this in why DRAM alone can’t keep up with AI anymore, because the obvious solution to a memory shortage would seem to be installing more memory. Unfortunately, at AI scale, that gets expensive very quickly and still doesn’t solve every bandwidth and capacity problem.

This is where the different layers of AI storage start making more sense. HBM can provide extraordinary bandwidth close to the processor. DRAM provides larger pools of fast working memory. NAND flash provides much greater persistent capacity. Each technology does something the others can’t do economically.

AI isn’t replacing one type of memory with another. If anything, it is forcing computers to use more types of memory at the same time.

Why Hard Drives Are Still Critical for AI Infrastructure

This one might be my favorite contradiction in the whole AI hardware story.

We spend all this time talking about incredibly sophisticated GPUs, HBM, NVMe storage and advanced semiconductor manufacturing, and then sitting farther down the chain is technology based on spinning magnetic platters.

The hard drive is very much alive.

In why hard drives are still critical for AI infrastructure, we looked at the enormous amount of information AI companies need to retain. Training datasets, model checkpoints, backups, archives and other bulk data don’t all need to sit on expensive high-performance flash storage.

At some point economics takes over.

When you’re storing information by the petabyte, cost per terabyte becomes awfully important. Hard drives remain one of the most economical ways to provide enormous amounts of online storage. AI may represent some of the most advanced computing technology we’ve ever built, but apparently it still needs a really big closet to put everything in.

Why AI Is Moving Compute Closer to Storage

For decades, the normal computer architecture has been fairly straightforward: store the data somewhere, move it into memory, send it to the processor and do something with it.

That works beautifully until the amount of data being moved becomes enormous.

Our article about why AI is moving compute closer to storage looks at an interesting response to that problem. Instead of constantly moving huge datasets back and forth across a system, some architectures are beginning to move portions of the computation closer to where the data already lives.

There is a simple logic behind this. Moving data consumes time, bandwidth and power. If you can reduce the distance that data needs to travel, you can sometimes improve the efficiency of the entire system without simply throwing a faster processor at the problem.

This is another place where AI is changing the traditional definition of computer performance. The fastest component isn’t necessarily the answer. Sometimes the bigger improvement comes from moving less data.

KV Cache: The AI Memory Reservoir Keeping GPUs From Running Dry

KV cache sounds like one of those subjects you can safely ignore until you realize it helps explain why AI inference can consume such surprising amounts of memory.

When a language model generates a response, it doesn’t want to recalculate everything it already processed every time it produces the next token. The KV cache acts as a memory reservoir, retaining information from previous calculations so the model can reuse it.

That’s great for performance. It isn’t free.

As conversations become longer and more users interact with a model, KV cache requirements can grow dramatically. Once again, we arrive at the same AI hardware problem from a different direction: where do you put all this information, and how quickly can you get it back to the processor?

KV cache is a good example of why looking only at GPU specifications doesn’t tell you very much about the performance of an entire AI system.

Apparently We Keep Coming Back to Memory and Storage

When we wrote these articles, there wasn’t a plan to build an eight-part AI series. The subjects simply kept crossing paths with the technology we already follow.

That might actually be the interesting part.

Strip away the chatbots, generated images and futuristic predictions and artificial intelligence becomes a massive data-processing problem. Data needs to be stored. It needs to be moved. It needs to be placed into memory. It needs to reach processors fast enough to keep extremely expensive hardware busy.

Suddenly NAND, DRAM, HBM, hard drives, PCIe and storage architecture don’t sound like side topics. They’re part of the machinery making modern AI possible.

And lately we’ve started looking past even the hardware.

Our more recent article, The Biggest AI Bottleneck Isn’t Software – It’s Electricians, takes the story outside the server. Building AI infrastructure requires enormous amounts of electrical power, cooling and physical construction. At some point you can have the GPUs, memory and storage sitting on a loading dock and still have a problem: somebody has to build the infrastructure required to turn all of it on.

That is probably where our AI coverage will continue to go. Not chasing every new AI announcement, but following the places where AI bumps into storage, hardware and the physical realities of computing.

Because those are usually the parts of the story that interest us anyway.

This article originally appeared on GetUSB.info. Subscribe to GetUSB updates.