VCritical

It’s not Hyper-V — it’s the drivers!

Eric Gray — Fri, 12 Mar 2010 18:59:14 +0000

VMware vSphere experts know that the ESX architecture has a critical advantage over other hypervisors like Xen, KVM, and Hyper-V. Instead of relying on general-purpose third-party device drivers, VMware ESX comes with hardened, stress-tested drivers — ready for your toughest enterprise workloads.

Windows deserves applause for reliability improvements in recent years. Unfortunately, the most reliable Windows design will never be able to counteract the damage that can be inflicted by a misbehaving device driver. In fact, take a look at this slide from a Mark Russinovich TechEd session where he makes the point that the majority of Windows blue screens (BSODs) are caused by third-party drivers:

Experts agree — Windows reliability is a function of driver reliability.

What about those drivers included with Windows?

You might be under the impression that these third-party drivers are for off-brand NICs purchased from the clearance bin at Fry’s. That’s not exactly the case — plenty of drivers are included right on the Windows DVD.

Consider this recent situation detailed by Mark Wilson. He set up a Hyper-V test machine with some Intel PRO/100 NIC cards and when he plugged in an Ethernet cable — instant BSOD!

Mark’s conclusion:

It’s good to know that Hyper-V was not at fault here: sure, it shows that a rogue device driver can bring down a Windows system but that’s hardly breaking news…

Meanwhile, back at the datacenter

Microsoft Hyper-V poster child Crutchfield recently found that the Broadcom NICs embedded in every one of their Dell servers were randomly losing virtual switch bindings after upgrading to Hyper-V R2. Hello downtime!

The administrator left us with the following thoughts:

Currently, Microsoft doesn’t have a work around for this issue and nor is there an ETA for resolution. After all, it may not be Microsoft, but could very well be Broadcom.

So, what do we do? Well, in my configurations I can’t afford these little gotchas and I will be working only with my trusted Intel NIC’s for my virtual networks.

Uh, you might want to check with Mark Wilson first about Intel drivers and Hyper-V.

The chain breaks when the weakest link fails

Notice the consistent theme in these two scenarios? The administrators are not blaming Hyper-V, instead focusing on the third-party hardware and drivers. Folks, it just does not matter — a hypervisor failure is incredibly disruptive.

When selecting the foundation for your private cloud, will you choose a hypervisor based on a general-purpose OS that aims to support hundreds of hardware variations from across the spectrum? Or will you build on a rock-sold, purpose-built platform that is specifically designed to aggregate and pool resources in your datacenter?

Leave a Comment • Subscribe to RSS • Subscribe via Email • Follow Eric Gray on Twitter
More articles on: ESX, Hyper-V • Browse All Virtualization Content
It’s not Hyper-V — it’s the drivers! by Eric Gray © 2010 • VCritical

Pimp My Hypervisor

Eric Gray — Mon, 01 Mar 2010 15:19:41 +0000

I bet you never thought of Hyper-V as a tricked-out custom hypervisor — with one less layer than VMware ESX — but it is…

“Yo dawg, I heard you like Patch Tuesday, so I put Windows in your hypervisor so you can patch it while you virtualize!”

Inspired by a joke from Kendrick Coleman. With apologies to Xzibit.

Taking snapshots of VMware ESX 4 running in a VM

Eric Gray — Fri, 26 Feb 2010 19:08:38 +0000

Clearly, the capability introduced with VMware vSphere 4 that allows VMware ESX 4 to virtualize itself is a real crowd-pleaser.

However, one limitation that some have discovered while using this lab-testing technique is the lack of ability to use snapshots with virtual ESX systems. In fact, after taking a snapshot of a virtual ESX VM, you will see the system boot into the recovery shell like so:

Ouch.

Can we fix it?

I asked some super-smart engineers inside VMware about the issue, and of course they know all about it and how to make it work.

The solution is to enable an undocumented advanced configuration option on the physical ESX host like so:

In other words:

Log into the console of the physical VMware ESX 4 host
Run the following command: esxcfg-advcfg -s 1 /COW/PermitVmfsOnRedoHierarchy
Verify the setting with the “get” flag: esxcfg-advcfg -g /COW/PermitVmfsOnRedoHierarchy

Do I even need to say that this stuff is not supported by VMware Global Support Services (GSS)? Well, I just did.

Yes we can!

After executing that one command on your physical machine, take a snapshot and boot up your virtual ESX:

Everything works just like you need it to now — you can even create a snapshot hierarchy:

Now what?

Were you constrained by the lack of virtual ESX snapshots? What interesting things will you use this for?

Linux apps run directly on Windows with virtualization!

Eric Gray — Wed, 17 Feb 2010 12:09:52 +0000

Microsoft has done remarkable things with virtualization — unbelievable, some say.

One outstanding achievement is the way the Hyper-V architects managed to completely collapse the guest operating system layer directly into the hypervisor. Take a look at this diagram from a Microsoft Virtualization competitive brochure:

[Yes, it's that same brochure again.]

There are several key differences between Microsoft and VMware hypervisor architectures. While the hardware and applications layers are pretty straightforward, applications don’t run directly on hardware. As you are about to see, these two platforms take very different approaches when it comes to virtualizing workloads.

The VMware vSphere solution is to use a thin, high-performance virtualization layer that enables a single physical system to simultaneously host multiple virtual machines. Each of these virtual machines executes isolated instances of traditional guest operating systems — Windows, Linux, Solaris, Netware, etc.

Due to apparent technological advancements in Hyper-V, it is now possible to run applications of all kinds directly on that integrated Windows OS/hypervisor layer without the need for a guest operating system at all. This allows Microsoft to omit an entire layer from their virtualization architecture.

I’m sure you have seen various announcements about the exceptional support that Hyper-V has for Linux workloads. Without a guest operating system layer, one must logically conclude that Linux applications are actually running on the Windows/Hyper-V hypervisor integration directly. Spectacular!

I thought I’d test this technological breakthrough in the lab myself by running Postfix, a very popular Linux SMTP mail server, on Windows Server 2008 R2 with Hyper-V. According to the diagram above, Postfix is classified as an application — the third layer.

Now, in order to install Postfix, I have to interact with the second layer in the stack, which is the “Microsoft Operating System w/Virtualization.” Since I’m an RHCE, I decided to use a Red Hat Enterprise Linux package of Postfix, but we can all agree that SUSE Linux Enterprise Server 11 would work equally well. However, I would not recommend using Ubuntu packages since that distribution is not supported by Hyper-V. Another side benefit to this technique is the fact that Windows has great mouse support.

Just as one would do on a legacy Linux system, I opened a trusty command shell and installed the package like so:

This is the first step to getting Postfix installed and running. I do have to admit that it took a few additional troubleshooting steps in my case — most certainly unique to my environment, so I will spare the details.

In order to complete the Postfix implementation, you’ll need to edit several configuration files. Do not use Notepad for this, as it does not understand the peculiar format of these text files:

One would think that the virtualization layer could also dynamically accommodate for UNIX line formatting, but that evidently was not part of the design. Fortunately, this is a very minor issue since WordPad can be used without problem:

Once you have the basic configuration in place, restart the service and validate — telnet to port 25 and send a test email.

There you have it, amazing Hyper-V virtualization — same capabilities as VMware vSphere with 25 percent fewer layers!

Hypervisor Footprint Quiz

Eric Gray — Wed, 10 Feb 2010 22:44:54 +0000

Remember the hypervisor footprint debate? You know, the one where Microsoft Virtualization declares that it is nothing but VMware FUD to tout the benefits of a small-footprint hypervisor.

I just found another point of view on hypervisor footprint size — take a look at this excerpt:

Small footprint: any features not applicable to our specific … scenarios are removed. This guarantees that we do not have to worry about updating or fixing unnecessary code, meaning less churning or required reboots for the host. All critical code paths are also highly optimized for our … scenarios.

Any guesses where that came from? Must be more of that VMware FUD!

Actually, it was one of the Windows Azure design principles. Which makes sense if you think about it — vSphere, with small-footprint ESXi, is the perfect foundation for cloud computing.

Leave a Comment • Subscribe to RSS • Subscribe via Email • Follow Eric Gray on Twitter
More articles on: ESXi, footprint, Hyper-V • Browse All Virtualization Content
Hypervisor Footprint Quiz by Eric Gray © 2010 • VCritical

Win $2500 with your 1337 VMware ESXi scripting skillz

Eric Gray — Tue, 02 Feb 2010 18:37:28 +0000

VMware is currently running a VMware ESXi scripting contest. Top prize is $2500, which is not too shabby for doing something productive.

Check out the details and get scripting!

Hello Dynamic Memory?

Eric Gray — Tue, 02 Feb 2010 04:52:40 +0000

Looks like I was on to something a few weeks back when I showed how Microsoft had tried — but failed — to implement a feature that would allow Hyper-V R2 to accommodate the use of more virtual machine memory than available on the underlying physical host.

A screenshot of Dynamic Memory configuration in a post-RTM build of Windows Server 2008 R2 has surfaced in an article at Softpedia.

Listen… Do you hear that?

It’s the sound of Microsoft Virtualization curbing their criticism of memory overcommit.

Hat tip to Aidan Finn.

Hyper-V More Stable, Just as Mature as VMware vSphere?

Eric Gray — Thu, 21 Jan 2010 23:29:13 +0000

I just read a fascinating article on the Microsoft Virtualization blog from a special guest poster responding to the recent InformationWeek article that cited 9 reasons Hyper-V is not ready for the Enterprise.

The author worked extra hard to refute all 9 points — but I do admit being somewhat distracted by the gratuitous use of VMWare throughout. Evidently, proofreading — unlike immeasurable technology and services discounts — is not one of the benefits extended to guest posters these days, which is a shame.

The Microsoft Virtualization MVP tries to use most of the pages from the playbook, such as memory overcommit FUD:

Relying on a host to overcommit memory to support failover hosts is potentially dangerous and incorrect oversubscription leads to all VMs suffering from performance.

Have you ever had a VM suffer from performance? I have, and believe me — it’s not pleasant.

But here is a familiar line:

… I would never over commit my VM hosts in production.

Where have we heard that before? I almost forgot to mention that this guest poster is none other than Chris Steffen — the star of that now-infamous CIO Magazine article who once called VMotion a “gimmick” and said:

I don’t know what kind of environment other than QA or development, or in a staging environment you’d want to do [live migration], but it’s not going to be in any production environment I’m responsible for; it’s not going to be any environment dependent on any kind of SLA or performance requirements. The justification for the inherent risk just isn’t there.

But what does Mr. Steffen say now that Hyper-V has Live Migration? About what you’d expect — and more:

Also keep in mind that using the System Center suite, the Microsoft solution can Live Migrate VMs to other hosts due to situations that VMware servers cannot even monitor, such as CPU Power, Power Supply Failures, and Fibre Channel congestion.

There are a number of other gems in this convincing piece. Did you know:

Hyper-V is more stable than and at least as secure as VMWare [sic]
vSphere is just as new as Hyper-V

Yep, there is a full-day supply of Kool-Aid in that guest post.

Nice work, Microsoft Virtualization team. I’m not so sure this sort of thing helps your cause — please keep it up.

VCritical in the top vDozen at vSphere-land

Eric Gray — Tue, 19 Jan 2010 15:27:03 +0000

Dear Readers,

Thank you for supporting VCritical in the latest round of vSphere-land top virtualization blogs from Eric Siebert.

I am very pleased to be voted into the #12 slot among a huge selection of talented professionals, moving up one notch from my previous position at lucky #13.

The message is clear — I will continue writing about VMware and competitive topics and I very much appreciate your ongoing support!

Best regards,

Eric

The Truth About Hyper-V Memory Overcommit

Eric Gray — Wed, 13 Jan 2010 13:20:05 +0000

The ability to assign more memory to virtual machines than physically available on a host is called memory overcommit and is a major factor that contributes to higher VM density — running more virtual machines per host increases efficiency and reduces cost. VMware ESX has provided this feature for multiple generations, giving it an advantage over competing hypervisors.

The Cost Per Application Calculator makes it clear that investing in VMware vSphere 4 significantly reduces your datacenter hardware footprint and associated costs. Scott Drummonds, the VMware performance expert, recently explained how memory overcommit is the only way to effectively use all of the physical RAM in a hypervisor.

Each time this topic comes up, Microsoft revs up their marketing machine and responds like this:

Hyper-V is free, use your money to buy RAM upgrades instead of VMware vSphere licenses
Memory overcommit is risky, VMware tells customers to turn it off anyway

The truth is that Hyper-V will have memory overcommit the moment Microsoft figures it out. If that day ever does come, watch the messaging quickly change to the familiar, “our customers asked us to implement this…” line.

Why is it fair to make such a bold claim? Two words:

Dynamic Memory

It’s a little known fact that some of the early releases of Hyper-V R2 actually had a feature that allowed administrators to assign more RAM to virtual machines than was physically present on the host — “Dynamic Memory” a.k.a. memory overcommit.

We can look back and see what bloggers like Mark Wilson had to say:

Microsoft also spoke to me about a dynamic memory capability (just like the balloon model that competitors offer). I asked why the company had been so vocal in downplaying competitive implementations of this technology yet was now implementing something similar and Ward Ralston explained to me that this is not the right solution for everyone but may help to handle memory usage spikes in a VDI environment. Since then, I’ve been advised that dynamic memory will not be in the beta release of Windows Server 2008 R2 and Microsoft is evaluating options for inclusion (or otherwise) at release candidate stage.

And this blog provided more detail on the implementation:

In Hyper-V 1.0, physical memory was hard allocated to the VMs, but in 2.0 the pool of memory is dynamically allocated and removed based VM usage with no service interruption. Dynamically allocating memory to VMs can drastically improve host consolidation rates.

Hyper-V 2.0 VMs are configured with an initial RAM setting (how much the machine boots with) as well as minimum and maximum RAM values. Hyper-V then adds RAM using the Hot-Add function, and removes it using a balloon driver (for supported OSes).

For the visual learners in the crowd, take a look at this VM configuration dialog:

Note that this is nothing like Transparent Page Sharing in VMware ESX — Hyper-V VMs would actually be reconfigured using hot-add memory, so the guest operating systems must cooperate.

In an interview with Steven Bink, even Bob Muglia acknowledged the need for overcommit:

We talked about Vmware ESX and its features like shared memory between VMs, “we definitely need to put that in our product” later [Muglia] said it will be in the next release. Like hot add memory, disk and nic’s will be and Live migration of course, which didn’t make it in this release.

By the way, hot-add memory didn’t make it into Hyper-V R2, either — VMware ESX 4 has it today.

Quick Memory Overcommit?

Evidently, dynamic memory was not even up to the rigorous “Quick” standard and was dropped from the release train. Perhaps in some future edition of Hyper-V, Quick Memory Overcommit will be offered — with just a few seconds of VM downtime as RAM allocation is dynamically adjusted. But that’s just speculation.

Sour Grapes

Instead of finding a way to implement memory overcommit in Hyper-V R2, Microsoft has taken the alternate approach of attacking VMware and declaring the feature unnecessary, unsafe, or too expensive.

The fact is that memory overcommit is an extremely valuable capability and VMware ESX has had it all along. Some of the Linux-based hypervisors are starting to figure it out. Until Hyper-V finally adds the feature we’ll continue to hear how easy it is to simply buy more RAM.

How long can you afford to wait?