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How to format vSAN Disk Groups with a legacy format version (2146221)

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Purpose

This article provides steps to format a vSAN disk with a legacy version in order to maintain compatibility during the upgrade process.

You might experience compatibility issues while adding or replacing disks under these conditions:
  • The vSAN cluster is partly upgraded.
  • The vSAN cluster is upgraded but the disk groups are not upgraded.
  • The vSAN cluster contains mixed host versions.
  • The disk format version in use by one or more hosts in the cluster is older than the latest installed version on the cluster.
Therefore, it is important to format new disks with the legacy version in order to maintain compatibility during the upgrade process. 

Resolution

It is generally recommended to continue with the vSAN on-disk upgrade process. However, if needed, you can format a vSAN disk group with a legacy version by adjusting the maximum possible on-disk format version by using an advanced-configuration parameter from the vSphere Client or the ESXi command line.

If incorrect-version disk groups have previously been created, these should be removed so the disk groups can be re-created with the correct version after implementing this procedure.

Notes
  • This procedure applies only for disk format versions native to vSAN 6.x. 
  • If the currently installed vSAN version is 6.x but the on-disk format is still version 1 (used by vSAN 5.5), see the procedure in Additional Information section.
  • If this configuration change is made, subsequent attempts to execute an on-disk format upgrade will fail unless the change is reverted and the original value is restored.
  • While a host has this setting change in effect, the vSAN Health Service may report an alarm indicating that the vSAN advanced configuration is not in sync. This is an expected behavior, and the alarm will clear after the default values are restored.

vSphere Client

  1. Log in to the vSphere Client.
  2. Select a host and then navigate to Manage > Settings > Advanced System Settings.
  3. Use the search box to look for Virsto.
  4. Identify the Virsto.DiskFormatVersion parameter and record its current value for later steps.
  5. Click the pencil icon to change the setting:


  6. Set the maximum on-disk format version based on the version used by other hosts in the cluster. For more information, see Understanding vSAN on-disk format versions (2145267).

    • If the host or other hosts use version 2.5 or a combination of versions 2.5 and 3 per vCenter Server, configure the maximum on-disk format version to 2.
      The disks are formatted to the newest version when the on-disk upgrade process is rerun.
    • If the host or other hosts use version 2 per vCenter, configure the maximum on-disk format version to 2.

  7. Replace or add disks as necessary.
  8. After disks have been added or replaced, revert these changes by restoring the original value identified in step 4.

ESXi Command Line

  1. Log in to the ESXi host via SSH or remote KVM console.
  2. Determine the current maximum on-disk format version:

    # esxcli system settings advanced list -o /Virsto/DiskFormatVersion

    For example:

    # esxcli system settings advanced list -o /Virsto/DiskFormatVersion
       Path: /Virsto/DiskFormatVersion
       Type: integer
       Int Value: 4
       Default Int Value: 4
       Min Value: 2
       Max Value: 4
       String Value:
       Default String Value:
       Valid Characters:
       Description: Virsto Disk Format version

  3. Set the maximum on-disk format version based on the version used by other hosts in the cluster, using this command:

    # esxcli system settings advanced set -i <desired version> -o /Virsto/DiskFormatVersion

    For more information on the vSAN on-disk format version, see Understanding vSAN on-disk format versions (2145267).
    • If the host or other hosts use version 2.5 or a combination of versions 2.5 and 3 per vCenter Server, configure the maximum on-disk format version to 2.
      The disks are formatted to the newest version when the on-disk upgrade process is rerun.
    • If the host or other hosts use version 2 per vCenter, configure the maximum on-disk format version to 2.

    For example:

    # esxcli system settings advanced set -i 2 -o /Virsto/DiskFormatVersion

  4. Replace or add disks as necessary.
  5. After disk-replacement activities are completed, return the parameter to the original value from step 1:

    # esxcfg-advcfg -s <original version> /Virsto/DiskFormatVersion

    For example:

    # esxcli system settings advanced set -i 4 -o /Virsto/DiskFormatVersion

Additional Information

If the currently-installed vSAN version is 6.x but the on-disk format is still version 1 (used by vSAN 5.5), the above procedure will not work. To format disks using on-disk version 1 when the ESXi hosts are 6.0 or above, Virsto must be disabled altogether to enforce the v1 on-disk format. Like the procedure outlined above, this can be accomplished via the vSphere Client or the ESXi command line.

vSphere Client

  1. Log in to the vSphere Client.
  2. Select a host and then navigate to Manage > Settings > Advanced System Settings.
  3. Use the search box to look for Virsto.
  4. Identify the Virsto.Enabled parameter.
  5. Click the pencil icon to change the setting.
  6. Disable Virsto functionality by changing the value of Virsto.Enabled to 0.
  7. After disks are added or replaced, revert these changes by restoring the original value of 1.

ESXi Command Line

  1. Log in to the ESXi host using SSH or remote KVM console.
  2. Disable the Virsto functionality to enforce the 5.5-compliant disk version:

    # esxcli system settings advanced set -i 0 -o /Virsto/Enabled

  3. Replace or add disks as necessary.
  4. After disk-replacement activities are completed, re-enable Virsto functionality:

    # esxcli system settings advanced set -i 1 -o /Virsto/Enabled

Tags

Legacy Format Version, vSAN upgrade compatability, on disk format

See Also

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