Upgrading current system (new m/b cpu ram) currently have a single 250gb SSD as cache in running system. 

 

New motherboard has 1 Fast NVME m.2 slot, and a slower m.2 slot. 

 

My initial thought was - buy 2 slower m.2 drives (500gb) and put them in a cache pool - then stick the old 250gb ssd in as an unassigned drive - job done. 

 

Then i got thinking that i was wasting the speed of theNVME slot, so should i put a fast single m.2 in the NVME slot, and then buy a second 250gb 2.5 SSD to match the existing - put the 2 2.5 SSDS in a cache pool, and then have the NVME as an unassigned drive that will be fast

 

Or do i just put in 2 slower ssd's on the motherboard m.2 slots, add in the existing 250gb 2.5 SSD, and pool all of them

 

Cache used as a download folder for sabnzb before getting moved to the array as part of sonar and radar, docker image is here, and a couple of VM's

I would just get one fast quality nvme m.2 the size you need/want for the cache. Then use your existing 250gb ssd to passthrough to vm or to use as unassigned drive. If you need more in future then add the slower m.2 for another vm or unassigned drive use.

cheers - so don't bother with a cache pool then?

8 minutes ago, rorton said:

cheers - so don't bother with a cache pool then?

No because a single pciex4 nvme m.2 will be much faster than ssd's in a cache pool and have plenty of I/O. Then your cache will be xfs which is much more stable and resilient than if you were to do a cache pool which would be btrfs. Just make sure you back up your cache regularly, can use plugin for that. This way also you can put more money towards a larger quality pciex4 nvme m.2 instead of spending elsewhere.

Ok cheers. I’m using the plugin to backup app data already, need to see how vm backups can be automated.  No idea why, but my current cache as a stand-alone is formatted as btrfs  

Cheers. I’m in the uk unfortunately. I was looking at that drive though on amazon, I may go for the 512gb model. Read.write says around 3000MB/s, unraid handles that ok?

You can use vm_settings_backup script in the user scripts plugin. This script will copy all vm xml and ovmf nvram into a dated vmsettings folder
to backup location set in script. Plus you can also follow spaceinvaderone to backup:

 

11 minutes ago, rorton said:

No idea why, but my current cache as a stand-alone is formatted as btrfs  

To change the cache filesystem you have to stop the array and click on cache to change filesystem for a single cache drive when you install new cache drive. Just make sure you move your cache to the array first so you don't lose it and then move it back to the new cache.

https://wiki.unraid.net/Replace_A_Cache_Drive