How to replace vSAN cache disk via vSphere Web Client

You need to back up the data before performing this step.

Table of Contents
1.　How to Replace a Cache Disk
2.　Additional Information: Unable to Remove Disk Group

How to Replace a Cache Disk

If the problem occurred on the cache disk, it will be a disk group level problem.
Therefore, the disk group needs to be recreated.

Depends on the version, the disk group icon may not appear on the vSphere Web Client even the problem occurred on a cache disk. In this case, please refer to the steps described in the below section.

Replacement Steps

1. Click the icon on the top of vSphere Web Client to switch to the maintenance mode.
   It is recommended to switch to the maintenance mode before replacement unless there is a special reason.
   Please refer to the Place a Member of vSAN ClusterinMaintenance Mode for switching to maintenance mode, and its types.

2. Click the icon at the top to remove the appropriate cache disk.
   Removing the cache disk will eventually remove the disk group.

3. Replace the applicable cache disk physically.

4. After the replacement, click the Add icon at the top of vSphere Web Client.
   

• Select a cache disk from the upper list, a capacity disk from the lower list and click OK.
  

• Once the created disk group is displayed, release the maintenance mode.
  

• Confirm the capacity of the recreated disk group is added to the capacity of the vSAN data store.

• Since alerts will remain even if the problem is solved, click Confirm or Reset to Green to delete manually.
  

Additional Information

Unable to Remove Disk Group
The disk group icon may not be displayed on the vSphere Web Client or removal of the disk group may be failed.
In that case, please try the following steps.

1. Connect to the applicable host via SSH.

2. Confirm "mpx.vmhbax:Cx:Tx:Lx" of capacity disk by running command esxcli vsan storage list or vdq -q -H.

3. Remove the mpx.vmhbax:Cx:Tx:Lx of the applicable capacity disk individually by running command esxcli vsan storage remove --evacuation-mode=noAction --disk=mpx.vmhbax:Cx:Tx:Lx.
   Example: esxcli vsan storage remove --evacuation-mode=noAction --disk= mpx.vmhba1:C0:T4:L0

4. Replace the cache disk physically and create a disk group on the vSphere Web Client.

Now you will be able to select the replaced cache disk and the existing capacity disk which is removed.