Hello there, everyone!
This post is about the procedure of disabling the ATS heartbeat in the ESXi. Please see below for more details.
DIAGNOSTIC
An ESXi 5.5 Update 2 or ESXi 6.0 host loses connectivity to a VMFS5 datastore, while using the VAAI ATS heartbeat in your environment.
Note: For additional symptoms and log entries, see the Additional Information section.
CAUSE
A change in the VMFS heartbeat update method was introduced in ESXi 5.5 Update 2, to help optimize the VMFS heartbeat process. Whereas the legacy method involves plain SCSI reads and writes with the VMware ESXi kernel handling validation, the new method offloads the validation step to the storage system. This is similar to other VAAI-related offloads.
This optimization results in a significant increase in the volume of ATS commands the ESXi kernel issues to the storage system and resulting in increased load on the storage system. Under certain circumstances, VMFS heartbeat using ATS may fail with false ATS miscompare which causes the ESXi kernel to again verify its access to VMFS datastores. This leads to the Lost access to datastore messages.
Notes:
For VMFS5 datastores, ATS heartbeat setting is on by default.
For VMFS3 datastores, ATS heartbeat setting is off by default.
RESOLUTION
To solve this issue, revert the heartbeat to non-ATS mechanisms by disabling ATS heartbeat on ALL hosts sharing the datastore where these errors are seen.
Notes:
If you suspect that ATS Heartbeat may be causing an issue with array workload or IO responsiveness, engage with your storage vendor to determine if they recommend disabling this function.
This change disables or enables using ATS primitive for creating or updating VMFS heartbeat and does not change ATS primitive configuration itself.
These operations can be safely performed online, while the storage is in use.
CAUTION
Disabling the ATS heartbeat:
Does not impact Acquiring a HB slot (starting heartbeat).
Periodic/Routine heartbeat updates are affected by this change.
Reverts the heartbeat related activity in the ESXi host using plain SCSI reads and writes to update its heartbeat on VMFS datastores.
For VMFS5 and VMFS6 datastores
To disable the ATS heartbeat, run either the CLI command or the PowerCLI command:
Command line:
# esxcli system settings advanced set -i 0 -o /VMFS3/UseATSForHBOnVMFS5PowerCLI:
Get-AdvancedSetting -Entity VMHost-Name -Name VMFS3.UseATSForHBOnVMFS5 | Set-AdvancedSetting -Value 0 -Confirm:$false
To enable ATS heartbeat, run either the CLI command or the PowerCLI command:
Command line:
# esxcli system settings advanced set -i 1 -o /VMFS3/UseATSForHBOnVMFS5PowerCLI:
Get-AdvancedSetting -Entity VMHost-Name -Name VMFS3.UseATSForHBOnVMFS5 | Set-AdvancedSetting -Value 1 -Confirm:$false
To review the results of changing options, run this command:
For example:
# esxcli system settings advanced list -o /VMFS3/UseATSForHBonVMFS5
You see output similar to:
Path: /VMFS3/UseATSForHBOnVMFS5
Type: integer
Int Value: 0 <--- check this value
Default Int Value: 1
Min Value: 0
Max Value: 1
String Value:
Default String Value:
Valid Characters:
Description: Use ATS for HB on ATS supported VMFS5 volumes
For VMFS3 datastores
To disable the ATS heartbeat, run either the CLI command or the PowerCLI command:
Command line:
# esxcli system settings advanced set -i 0 -o /VMFS3/UseATSForHBOnVMFS3PowerCLI:
Get-AdvancedSetting -Entity VMHost-Name -Name VMFS3.UseATSForHBOnVMFS3 | Set-AdvancedSetting -Value 0 -Confirm:$false
To enable ATS heartbeat, run either the CLI command or the PowerCLI command:
Command line:
# esxcli system settings advanced set -i 1 -o /VMFS3/UseATSForHBOnVMFS3PowerCLI:
Get-AdvancedSetting -Entity VMHost-Name -Name VMFS3.UseATSForHBOnVMFS3 | Set-AdvancedSetting -Value 1 -Confirm:$false
Notes:
This change takes effect immediately without rebooting.
This change does not affect ESXi host OS.
The root node of these options is /VMFS3 regardless of the VMFS version. The last character of the option matches the corresponding VMFS version.
To review the results of changing options, run this command:
# esxcli system settings advanced list -o /path
For example:
# esxcli system settings advanced list -o /VMFS3/UseATSForHBonVMFS3
You see output similar to:
Path: /VMFS3/UseATSForHBOnVMFS3
Type: integer
Int Value: 0 <--- Check this value
Default Int Value: 0
Min Value: 0
Max Value: 1
String Value:
Default String Value:
Valid Characters:
Description: Use ATS for HB on ATS supported VMFS3 volumes
This reversion of VMFS heartbeat activity is preferred instead of globally disabling VAAI or ATS when using applicable storage systems. Although some storage systems require that the heartbeat-related activity be reverted to the legacy methodology, they still handle non-heartbeat-related ATS commands normally and there are dramatic performance and scale benefits to the use of ATS even if ATS should not be used for VMFS heartbeats.
Related information
You experience these additional symptoms:
In the /var/run/log/vobd.log file and Virtual Center Events, you see the VOB message:
Lost access to volume <uuid><volume name> due to connectivity issues. Recovery attempt is in progress and the outcome will be reported shortlyIn the /var/run/log/vmkernel.log file, you see the message:
ATS Miscompare detected between test and set HB images at offset XXX on vol YYYIn the /var/log/vmkernel.log file, you see similar error messages indicating an ATS miscompare:
2015-11-20T22:12:47.194Z cpu13:33467)ScsiDeviceIO: 2645: Cmd(0x439dd0d7c400) 0x89, CmdSN 0x2f3dd6 from world 3937473 to dev "naa.50002ac0049412fa" failed H:0x0 D:0x2 P:0x0 Valid sense data: 0xe 0x1d 0x0.You may also see:
Hosts disconnecting from vSphere vCenter.
Virtual machines hanging on I/O operations.
Note: These symptoms are seen in connection with the use of VAAI ATS heartbeat with storage arrays supplied by several different vendors.
This issue is not limited to one vendor. If the datastores are on IBM Storwize and San Volume Controller, the ATS heartbeat must be disabled per IBM recommendation. For more information, see the IBM advisory Host Disconnects Using VMware vSphere 5.5.0 Update 2 and vSphere 6.0.
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