I know the parity drive is the cornerstone of Unraid, but what if there's only 2 HDDs in a SFF build, and there might be issues with running a parity drive?

 

My build is a mini-ITX, with only 4 SATA ports (plus m.2 slot). Currently there's 2 x 12TB HHDs, 1 X 1TB cache SSD, 1 BR drive, and a 500GB m.2 (older Windows drive). I hit many bumps in my first setup, as to be expected. The biggest one was copying data from a USB Drobo to Unraid. Using Krusader, it would either stall or freeze out the system. I checked all the BIOS settings specifically for Ryzen (global C-state, Power state, turned RAM speed down from 3000 to 2400), which maybe helped but I still encountered stalls. The best it would copy was 120GB. I also turned on turbo write mode. In a last ditch effort, I unplugged a keyboard (I did get weird USB cable fails messages on startup) and disabled the parity drive. This morning Santa delivered, Krusader is copying over perfectly!

 

So between the issues transferring from an Unassigned device (to a non-cache share), but also really slow speeds transferring data over the network to another share (cache, 50gb took hours), and given there aren't multiple drives to protect at this time, I'm wondering if there's issues with the onboard SATA controller. And if that's the case, maybe there's an alternate way to set this up, like just running a sync between the drives? I'm open to suggestions, especially on tests to run. I'm new at this, so any help is appreciated.

I am looking to build a SFF unraid server and, as i have everything backed up elsewhere that needs backing up, i wont be adding a parity drive (at least for the foreseeable).

 

This would be used as a stable plex machine. And my 8 drive monster will be for other media and to play with VMs and Dockers. This again does not yet have a parity drive. But again i have the data backed up. Before UnRaid i stored everything on portable HDDs, which are now my backups.

 

Parity is a very good idea, but it isn’t necessary.

I really do want the 2nd drive to be a backup/mirror of the first. I just don't know if it's worth setting it up as a parity with the supposed performance hit I hear about (vs mirrored drives). Although my cache drive is plenty big, so I doubt I would even notice. I know it would make expansion easy, but expansion in my case involves a new mobo/case. That's why I wonder if there is an alternate way to set up 2 HHDs. I'm having enough GPU issues, where I'm starting to question the whole thing.

Don’t install the second drive and keep it as a backup away from the server. Then when you need to expand, buy two more drives, fit one to the server and use the other as a backup for it.

 

i keep my backups away from the server.

8 hours ago, TheDaveAbides said:

I really do want the 2nd drive to be a backup/mirror of the first. I just don't know if it's worth setting it up as a parity with the supposed performance hit I hear about (vs mirrored drives). Although my cache drive is plenty big, so I doubt I would even notice. I know it would make expansion easy, but expansion in my case involves a new mobo/case. That's why I wonder if there is an alternate way to set up 2 HHDs. I'm having enough GPU issues, where I'm starting to question the whole thing.

You need to have an Array to start Docker or VM services. But you don't have to actually use the Array.

If one (or several) Pool(s) suits you better, you add a cheap USB flash drive as the only data drive in the Array and only run of the Pools.

 

You could use your 2 12TB HDDs in one BTRFS RAID1 pool.

 

Note that you cannot use one Pool as 'cache' for another Pool used as 'storage'. But you could use one as data and the other as fast storage for dockers, VMs, etc.

Those limitations might change in the future though, the current multiple Pools and the future multiple Arrays will require changes in the Mover behavior. Not much details or deadline for the moment.

16 hours ago, TheDaveAbides said:

I really do want the 2nd drive to be a backup/mirror of the first. I just don't know if it's worth setting it up as a parity with the supposed performance hit I hear about (vs mirrored drives).

For the special case of parity and a single data disk, parity is a mirror of the data disk.