Potential DS8100/DS8300/DS8700/DS8800 loss of access issue when running VMWare 4.1 or higher with vStorage API for Array Integration ( VAAI ) Zero Blocks/Write Same enabled

Content

IBM has received reports of issues when running VAAI Zero Blocks/Write Same commands with DS8000 that have caused application problems including a loss of access to data. Clients are advised to disable VAAI's use of the Zero Blocks/Write Same command to avoid the possibility of an issue, and the procedure to do so is described in the Mitigation and Resolution/Support information below.

Mitigation
To avoid any issues, use the following to disable the Zero Blocks/Write Same function of VAAI (HardwareAcceleratedInit parameter). Other functions of VAAI may remain enabled for use on other storage systems. All OTHER non VAAI features of VMWare ESX 4.1 or higher are certified with DS8000 (all models) and function normally.

Here's a KB for disabling the Zero Blocks/Write Same command. - http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=1033665

Note: Each time the VMWare software is updated, the write same capability is reset to "enabled", so this mitigation needs to be repeated. To permanently eliminate the exposure to this issue, all DS8000s connected to hosts using VMWare need to be updated to the appropriate firmware identified below in the Resolution/Support section.

Resolution/Support
The DS8000 has firmware now available that blocks the write same commands, resulting in VMWare reverting to normal SCSI writes, and eliminating the loss of access risk described above. This fix is available in the following code bundles:

DS8100/DS8300: 64.36.48.1 or higher
DS8700 on release 6.2 code: 76.20.98.1 or higher
DS8700 on release 6.3 code: 76.31.17.0 or higher
DS8800 on release 6.2 code: 86.20.121.1 or higher
DS8800 on release 6.3 code: 86.31.26.0 or higher

More Information on VAAI
Here's a description on VAAI - http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=1021976

VAAI uses these fundamental operations:

* Atomic Test & Set (ATS), which is used during creation of files on the VMFS volume
* Clone Blocks/Full Copy/XCOPY, which is used to copy data
* Zero Blocks/Write Same, which is used to zero-out disk regions
* Thin Provisioning in ESXi 5.x and later hosts, which allows the ESXi host to tell the array when the space previously occupied by a virtual machine (whether it be deleted or migrated to another datastore) can be reclaimed.