I currently have a single nvme drive in my cache pool with 723 GB of data on it. I've recently installed a second nvme drive, with the intention of adding it to the cache pool. I took the array offline, set the cache pool to two slots, and added my new drive to the pool. When I attempted to bring it back online, I received the error in the subject.

I previously read this post with a similar error message, but it wasn't 100% clear to me if its the exact same problem or if there may be a different solution now. Is deleting and recreating the cache pool the right move? Should I be trying to use the mover to clear out the cache first?

Thanks in advance for any advice you might have.

Matt

tower-diagnostics-20250925-1841.zip

You cannot expand an XFS pool, they are single device only. You will need to backup and reformat to btrfs or ZFS.