SSD cache and unprotected shares

[paaland]

New to unRAID, but have used other NAS software like Qnap before. I have two data disks, one parity disk and a cache SSD.

I've tried reading the FAQ, but I'm still not getting it.

 

Of my shares, only isos and my home folder share is marked green and protected. These have use cache set to "yes" which I understand means that writes happens to the cache first, then the mover process moves them to the array when it runs.

 

Other shares like appdata (docker), domains (vms) and system are marked "unprotected". These have also use cache set to "yes". Is the mover not able to move files if in use? Do I need to shut down containers and vms to move them? If so, what's really the point of the cache?

 

What happens when the cache disk is full? Some kind of LRU or FIFO or will I start getting write errors?

Edited December 15, 2020 by paaland

[trurl]

13 minutes ago, paaland said:

appdata (docker), domains (vms) and system are marked "unprotected". These have also use cache set to "yes". Is the mover not able to move files if in use? Do I need to shut down containers and vms to move them?

Mover can't move open files, but you really want these shares set to cache-prefer and keep all their files on cache. Having them on the array will impact docker/VM performance due to slower parity, and will also keep array disks spunup.

 

You can make cache protected by creating a btrfs raid1 cache pool, or you can protect these shares by backing them up using CA Backup plugin or other means.