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ESXi 5.0 hosts fail to mount VMFS5 volumes that are formatted with ATS-only capabilities

Cause

When a VMFS-5 volume formatted on a VAAI capable device it will use ATS locking exclusively termed as ATS only. To check if a VMFS volume has been configured with ATS only use the following command:

# vmkfstools -Ph -v1 /vmfs/volumes/

The output will look similar to:

VMFS-5.54 file system spanning 1 partitions.
File system label (if any): ats-test-1
Mode: public ATS-only

When an ESX server discovers and registers new and existing devices the VAAI plugin module is loaded if the device is deemed to be VAAI capable during PSA device registration, in this particular case the ESX may fail to register device correctly with VAAI plugin module as we are not reading the capacity of the volume correctly to apply the equivalent VAAI pluging module. As a result the VMFS5 volume may fail to mount.

This issue is seen to occur in, but is not restricted to, EMC arrays Clariion CX4, NS, and VNX arrays.

Resolution

VMware is aware of this issue.

To workaround this issue in ESXi versions prior to ESXi 5.0, disable VAAI ATS locking mechanism on your hosts:
  1. Check if VAAI features are enabled on the ESXi 5.0 host from a console or SSH session using this command:

    # esxcli system settings advanced list -o /VMFS3/HardwareAcceleratedLocking

    You see an output similar to:

    Path: /VMFS3/HardwareAcceleratedLocking
       Type: integer
       Int Value: 1
       Default Int Value: 1
       Min Value: 0
       Max Value: 1
       String Value:
       Default String Value:
       Valid Characters:
       Description: Enable hardware accelerated VMFS locking (requires compliant hardware)


    The Int Value of 1 is indicating that VAAI features are enabled.

  2. Disable Hardware Accelerated Locking to ensure that the VMFS datastores are stable on the cluster:

    1. Log in to vCenter Server 5.0 or ESXi 5.0 host using the vSphere Client.
    2. In the vSphere Client inventory panel, choose the ESXi 5.0 host.
    3. Click the Configuration tab, then click Advanced Settings under Software.
    4. Change the value of this parameter to 0:

      VMFS3.HardwareAcceleratedLocking

      Alternatively this can be disabled from the console with the command:

      # esxcli system settings advanced set -i 0 -o /VMFS3/HardwareAcceleratedLocking

  3. Verify that VAAI has been disabled using the esxcli again:

    # esxcli system settings advanced list -o /VMFS3/HardwareAcceleratedLocking

    You see an output similar to:

    Path: /VMFS3/HardwareAcceleratedLocking
       Type: integer
       Int Value: 0
       Default Int Value: 1
       Min Value: 0
       Max Value: 1
       String Value:
       Default String Value:
       Valid Characters:
       Description: Enable hardware accelerated VMFS locking (requires compliant hardware)

       
    The Int Value of 0 is indicates that VAAI features are disabled.

Note: EMC Clariion CX4 series arrays are not currently supported for VAAI Block Hardware Acceleration Support on vSphere ESXi 5.0. For more/related information, see EMC CX and VNX Firmware and ESX requirements for vStorage APIs for Array Integration (VAAI) support (2008822).
Based on VMware KB 2006858

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