IBM Support

Potential Loss of Access When Using VMware VAAI Atomic Test-and-Set With V6.4.1.x Levels Earlier Than V6.4.1.4

Flash (Alert)


VMware hosts using the Atomic Test-and-Set feature of the VAAI API with Storwize or SAN Volume Controller V6.4.1.x levels earlier than V6.4.1.4 may experience an issue that can cause multiple node or node canisters to reboot, potentially leading to temporary loss of host access.


VMware hosts configured to use the Atomic Test-and-Set (ATS) feature of the VAAI API employ SCSI Compare and Write to control locking on Storwize and SAN Volume Controller volumes.

An issue exists in the handling of Compare and Write commands in V6.4.1.x releases earlier than V6.4.1.4 that can lead to multiple nodes rebooting simultaneously, which may cause a temporary loss of access to volumes presented by these nodes.

Customers are advised not to use the VMware ATS feature if they are running an affected release.

Please refer to VMware support documentation for instructions on how to disable the ATS feature.


This issue was resolved by APAR IC90455 in the V6.4.1.4 PTF release.

Important: The probability of experiencing this issue is increased during a system upgrade. It is therefore strongly recommended to disable ATS on all VMware hosts before upgrading from an affected release to V6.4.1.4 or higher.

Cross reference information
Segment Product Component Platform Version Edition
Storage Virtualization SAN Volume Controller 6.4 SAN Volume Controller 6.4
Disk Storage Systems IBM Storwize V3500 (2071) 6.4
Disk Storage Systems IBM Storwize V3700 (2072) 6.4
Disk Storage Systems Flex System V7000 6.4

Document information

More support for: IBM Storwize V7000 (2076)

Version: 6.4

Operating system(s): IBM Storwize V7000

Reference #: S1004343

Modified date: 16 May 2013

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