RAID-Z or Mirroring?

[amizzo]

Hi guys,

So I'm still trying to wrap my head around ZFS. While it's most likely overkill for my needs (media / time machine server), I really like the features of ZFS and wanted to build a NAS around it.

I have 2x 1TB hard drives, and 2x 2TB hard drives. What would be the best way to set up FreeNas/ZFS to optimize resources? Should I set up two pools, each with 1x 1TB and 1x 2TB drive, and mirror them? From my (limited) understanding I don't think RAID-Z would be optimal for this situation (because of an even number of drives in non-equal sizes) but I'm not sure. Basically I'd like to have protection from a single hard drive failure, and be able to swap in a replacement hard drive to fix the problem. Also, I'd like to be able to (eventually) replace the 1TB hard drives with 2TB hard drives (in the future).

Thanks in advance for your help guys!

 

[jgreco]

Mirror the two 1TB drives. Mirror the two 2TB drives. You can place both resulting vdev's in the same pool for a total of 3TB, or two separate pools.

You could stick all four drives in a RAIDZ, but you would lose 1TB on each of the two 2TB drives, and you'd still wind up with 3TB usable space: four 1TB component disks minus one for parity. And RAIDZ doesn't perform anywhere near as well as mirroring.

 

[survive]

Hi amizzo,

If you plan on swapping the 1TB drives for 2TB drives in the future then raidz might be the way to go. I suppose you could also do the same thing if you striped each pair of drives into a pair of virtual devices and put both vdevs into single pool, but once you did the 1TB -> 2TB swap you would wind up with ~3.6TB instead of ~5.4TB, but the pool should perform better.

-Will