Cache drive reconfiguration in Server 2025 Storage Spaces Direct cluster

To eventually answer my question, yes it is possible to reconfigure the cache drives without completely rebuilding the S2D storage.

Prior to doing the work on our production cluster, I built a small test cluster to replicate the setup.

This was set up with all disks originally on a RAID controller in HBA mode.

I then swapped the RAID controller for a HBA in one node, to simulate what I planned to do on the production cluster in changing the bus type. In this case from RAID to SAS. This all worked without issues. The disks were still recognised correctly in S2D, with the cache/journal disks working as expected.

Yesterday, I reconfigured the production cluster, moving the NVMe cache disks from the RAID card to be directly connected to the PCIe bus on the system board, changing the bus type in S2D from SAS to NVMe.

Everything came up as expected without issues. This was done one node at a time, keeping the cluster up throughout. All disks were still correctly recognised in S2D and the cache working correctly.

If you're doing something other than changing the bus type, then I suspect doing some of the steps mentioned by Darryl van der Peijl​  would be required.

The Get-CacheDiskStatus powershell scripts from his link https://www.darrylvanderpeijl.com/storage-spaces-direct-cache-disk-status/ was very useful to prove that the cache disks were still being used correctly.

Cheers

Rob