Currently I have an array with 1x disk and 1x parity. I also have a cahce pool with a single SSD. Unfortunately, the cache SSD started reporting read errors, thus I want to add a parity drive to the cache pool before it totally fails.

Before I start I want to be sure on the procedure. From https://wiki.unraid.net/Manual/Storage_Management#Pool_Modes I guess the proper procedure is:

• Backup pool to array using 'mover'
• Add extra disk to pool
• Restore pool using 'mover'

And when this is up an running, I guess I can replace the failing SSD?

 

Note: I have everything backed up, so if I f*** this up, I can always restore, but I would perfer to add parity before restoring my backup.

Parity only applies to the main array, not to pools.

 

Pools can be configured with various BTRFS RAID levels, but I don't think it's wise to attempt to expand a pool that currently has errors, you will probably end up worse off than before. I think your best option is to follow the replace cache disk procedure, which does entail using the mover to send the data to the main array by setting any cache prefer or only shares to cache yes, and running the mover. Typically you would need to disable the docker engine and VM services in the configuration so their tabs are gone from the GUI before you run the mover.

 

Attach diagnostics to your next post in this thread for better educated opinions.