Replace a Flash Caching Device on a Host

You should replace a flash caching device if you detect a failure or when you must upgrade it. Before you physically unplug a flash device from the host, you must manually remove the device from Virtual SAN.

Caution: If you decommission the flash caching device without removing it from Virtual SAN first, Virtual SAN uses smaller amount of cache than expected. As a result, the cluster performance becomes degraded.

When you replace a flash caching device, the virtual machines on the disk group become inaccessible and the components on the group are marked as degraded. See A Flash Caching Device Is Not Accessible in a Virtual SAN Cluster.

Prerequisites

Verify that the storage controllers on the hosts are configured in passthrough mode and support the hot-plug feature.

If the storage controllers are configured in RAID 0 mode, see the vendor documentation for information about adding and removing devices.
If you upgrade the flash caching device, verify the following requirements:
- If you upgrade the flash caching device, verify that the cluster contains enough space to migrate the data from the disk group that is associated with the flash device.
- Place the host in maintenance mode. See Place a Member of Virtual SAN Cluster in Maintenance Mode.

Procedure

In the vSphere Web Client, navigate to the Virtual SAN cluster.
On the Configure tab, click Disk Management under Virtual SAN.
Select the disk group that contains the device that you want to replace.
Select the flash caching device and click Remove selected disk(s) from disk group.

Results

After the flash caching device is deleted from the Virtual SAN cluster, the cluster details reflect the current cluster capacity and configuration settings. Virtual SAN discards the disk group memberships, deletes partitions, and removes stale data from all devices.

What to do next

Add a new device to the host.
The host automatically detects the device.
If the host is unable to detect the device, perform a device rescan.