I'm on 6.6 RC1.  I have a 2 disk (HDDs) cache pool which I want to replace with a cache pool of 2 SSDs which  I just added to my system.  The SSDs are currently recognized as unassigned disks. I intend to reassign the current 2 HDD disks in my cache pool as data disks.  I have several VMs on my cache pool as well as the system files (docker and libvirt) and docker app data files. I intend to (1) back up the VMs, app data and system directories to the array; (2) Stop the array and remove the current HDDs from the cache pool; (3) add the unassigned SSDs to the cache pool (which I assume will automatically be formated as BTRFS) (4) format the HDDs as XFS and add to the array; (5) Start the array and copy VMs, app data and system directories to new cache pool.  I assume when I restart the array, the VM and docker service will not start until after the system files are copied to the cache pool and I restart the array for the second time. Let me know if I'm missing something.  Thanks.

Edited September 4, 20186 yr by Woodpusherghd

If the SSDs are the same size or larger than the HDDs you could do an online replacement, but assuming they are smaller you can use this to help with the backup/restore part:

 

https://forums.unraid.net/topic/46802-faq-for-unraid-v6/?do=findComment&comment=511923

 

Thanks Johnnie.black.  I followed the steps in the link and I'm up and running.