How best to incorporate two SSDs into system

[klieber]

I'm new to unraid and setting up my first system.  I have 4 x 18TB HDDs, with one used as a parity drive.  That's all set up and working fine.  I also have 1 x 500GB SSD and 1 x 2TB SSD that I'm trying to figure out how best to incorporate.  Here's what I've done so far - any feedback welcome:

 

• Set up the 500GB SSD as a cache drive
• Set up the 2TB SSD as a member of the array (Disk 4)
• Configured the appdata and domains shares to only use Disk 4, excluding the other disks
• Configured the other shares to use Disks 1 - 3, but exclude Disk 4

 

My intent is to have all my docker containers and VMs run off of the 2TB SSD and then use the 500GB SSD as a general-purpose cache for the system.  I'm not entirely familiar with how Unraid uses the cache drive, however, so was curious if there is a better way to set things up.

 

Thanks.

[trurl]

SSDs in the parity array can't be written any faster than parity, and they can't be trimmed.

 

The latest Unraid 6.9 betas support multiple cache pools which would be perfect for what you have there. You could let the 2TB SSD cache user share writes, and use the 500GB SSD for appdata, domains, and system shares.

 

If you don't want to go with a beta you could put both SSDs in cache in btrfs single mode and so combine their capacities.

 

[klieber]

30 minutes ago, trurl said:

you could put both SSDs in cache in btrfs single mode and so combine their capacities.

 

Thanks for the pointers.  So to set it up the way you suggest, I would:

• remove the 2TB SSD from the array
• Move it to the cache pool
• Set the 'Use cache' option to 'Only' for the appdata and domain shares
• Ensure I regularly backup the cache pool, since that's not covered via the parity protection

Is that basically correct?

[itimpi]

13 minutes ago, klieber said:

Ensure I regularly backup the cache pool, since that's not covered via the parity protection

The CA Backup plugin can automate backing up the appdata share.

[trurl]