EMC Storage Product Knowledge Sharing

SRDF Pair Status

2009-09-16T12:56:00.000-07:00

SRDF/S and SRDF/A configuration involves tasks such as suspending and resuming the replication, failover from R1 side to R2, restoring R1 or R2 volumes from their BCV, and more. You perform these and other SRDF/S or SRDF/A operations using both symrdf and TimeFinder command symmir. The below details are for SRDF Pair states during SRDF procedure.

SyncInProg :- A synchronization is currently in progress between the R1 and the R2. There are existing invalid tracks between the two pairs and the logical link between both sides of an RDF pair is up.

Synchronized :- The R1 and the R2 are currently in a synchronized state. The same content exists on the R2 as the R1. There are no invalid tracks between the two pairs.

Split :- The R1 and the R2 are currently Ready to their hosts, but the link is Not Ready or Write Disabled.

Failed Over :- The R1 is currently Not Ready or Write Disabled and operations been failed over to the R2.

R1 Updated :- The R1 is currently Not Ready or Write Disabled to the host, there are no local invalid tracks on the R1 side, and the link is Ready or Write Disabled.

R1 UpdInProg :- The R1 is currently Not Ready or Write Disabled to the host, there are invalid local (R1) tracks on the source side, and the link is Ready or Write Disabled.
Suspended :- The RDF links have been suspended and are Not Ready or Write Disabled. If the R1 is Ready while the links are suspended, any I/O accumulates as invalid tracks owed to the R2.

Partitioned :- The SYMAPI is currently unable to communicate through the corresponding RDF path to the remote Symmetrix. Partitioned may apply to devices within an RA group. For example, if SYMAPI is unable to communicate to a remote Symmetrix via an RA group, devices in that RA group are marked as being in the Partitioned state.

Mixed :- Mixed is a composite SYMAPI device group RDF pair state. Different SRDF pair states exist within a device group.

Invalid :- This is the default state when no other SRDF state applies. The combination of R1, R2, and RDF link states and statuses do not match any other pair state. This state may occur if there is a problem at the disk director level.

Consistent :- The R2 SRDF/A capable devices are in a consistent state. Consistent state signifies the normal state of operation for device pairs operating in asynchronous mode.

Details about Symmetrix Optimizer

2009-08-24T09:35:00.000-07:00

Symmetrix Optimizer improves array performance by continuously monitoring access patterns and migrating devices to achieve balance across the disks in the array. This is process is carried out automatically based on user-defined parameters and is completely transparent to end users, hosts and applications in the environment. Migration is performed with constant data availability and consistent protection.

Optimizer performs self-tuning of Symmetrix data configurations from the Symmetrix service processor by:
· Analyzing statistics about Symmetrix logical device activity.
· Determining which logical devices should have their physical locations swapped to enhance Symmetrix performance.
· Swapping logical devices and their data using internal Dynamic Reallocation Volumes (DRVs) to hold customer data while reconfiguring the system (on a device-to-device basis).

Symmetrix Optimizer can be utilized via EMC Symmetrix Management Console or SYMCLI, where user can defines the following:

1) Symmetrix device to be optimized
2) Priority of those devices.
3) Window of time that profiles the business workload.
4) Window of time in which Optimizer is allowed to swap.
5) Additional business rules.
6) The pace of the Symmetrix Optimizer volume copy mechanism.

After being initialized with the user-defined parameters, Symmetrix Optimizer operates totally autonomously on the Symmetrix service processor to perform the following steps.

1) Symmetrix Optimizer builds a database of device activity statistics on the Symmetrix back end.

2) Using the data collected, configuration information and user-defined parameters, the Optimizer algorithm identifies busy and idle devices and their locations on the physical drives. The algorithm tries to minimize average disk service time by balancing I/O activity across physical disk by locating busy devices close to each other on the same disk, and by locating busy devices on faster areas of the disks. This is done by taking into account the speed of the disk, the disk geometry and the actuator speed.

3) Once a solution for load balancing has been developed the next phase to carry out the Symmetrix device swaps. This is don using established EMC Timefinder technology, which maintains data protection and availability. Users can specify if swaps should occur in completely automated fashion or if the user is required to approve Symmetrix device swaps before the action is taken.

4) Once the swap function is complete, Symmetrix Optimizer continues data analysis for the next swap.

How Symmetrix Optimizer works:-

1) Automatically collects logical device activity data, based upon the devices and time window you define.

2) Identifies “hot” and “cold” logical devices, and determines on which physical drives they reside.

3) Compares physical drive performance characteristics, such as spindle speed, head actuator speed, and drive geometry.

4) Determines which logical device swaps would reduce physical drive contention and minimize average disk service times.

5) Using the Optimizer Swap Wizard, swaps logical devices to balance activity across the back end of the Symmetrix array.

Optimizer is designed to run automatically in the background, analyzing performance in the performance time windows you specify and performing swaps in the swap time windows you specify.

Multipath Setting required for VMWare in SAN

2009-08-05T06:44:00.000-07:00

A multipath requirement for different storage arrays:-
All storage arrays: - Write cache must be disabled if not battery backed.
Topology: - No single failure should cause both HBA and SP failover, especially with active-passive storage arrays.

IBM TotalStorage DS 400 Family (formely FastT) –

Defaul host type must be LNXCL or Host Type must be LNXCL or
AVT (Auto Volume Transfer) is disabled in this host mode.

HDS 99xx and 95xx family – HDS 9500V family (Thunder)- Requires two host modes:
Host mode 1 – standard
Host mode 2 – Sun Cluster
HDS 99xx family Lightning and HDS Tamba USP requires host mode set to Netware.

EMC Symmetrix :- Enable the SPC2 and SC3 settings.

EMC CLARiiON – All initiator records must have

- Fail-over Mode = 1
- Initiator Type = “CLARiiON Open”
- Array CommPath = “Enabled” or 1

HP EVA :- For EVA3000/5000 firmware 4.001 and above and EVA 4000/6000/8000 firmware 5.031 and above, set the host type to VMWare. Otherwise, set the host mode type to custom. The value is :
EVA3000/5000 firmware 3.x: 000000002200282E
EVA4000/6000/8000: 000000202200083E

HP XP:- For XP 128/1024/10000/12000, the host mode should be set to 0C (Windows), that is, zeroC (Windows).

NetApp :- No specific requirements

ESX Server Configuration :- Set the following Advanced Settings for the ESX Server host:-

Set Disk.UseLunReset to 1
Set Disk.UseDeviceReset to 0
A multipathing policy of Most Recently Used must be set for all LUNs hosting clustered disks for active-passive arrays. A multipathing policy of Most Recently Used or Fixed may be set for LUNs on active-active arrays. All FC HBAs must be of the same model.