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Optimal Pool Layout for 10-12 drives, WD RED 10TB drives, for Plex

Feb 21, 2019
The title pretty much says it all.

Back in February, I built my first ever NAS (also my first ever NAS, period). It is based upon a Supermicro X9SRL-F, E5 2630L v2, 24GB DDR3 ECC RAM, and currently running 9x4TB WD REDs, configured as one ZFS2 pool. This gives me about 25TB of usable space, of which I have already used about 20TB.

The server is almost exclusively used for Plex, both local and remote streaming.

I am therefore looking to upgrade. I am planning on buying 10TB white label WD REDs, and need help determining the best layout for the pool. Data loss prevention is of course my primary focus, but I don't want to waste unnecessary space. Also, my tower (Fractal Design Define R6) can "only" fit 11 drives natively, allthough, it should be easy to modify it to fit 12 drives.

Would you recommend i.e. 3 pools of 4 drives running ZFS1, or maybe 1 large pool running 8-10 drives in a ZFS2 config?


FreeNAS Experienced
Feb 2, 2018
Hey Chris,

I would certainly NOT go with 3x RaidZ1. If you are about to get 3 drives for redundancy, better to go for 12 drives in a RaidZ-3. Yes a single vDev gives you the speed of a single drive, but nowhere you talked about any performance problem.

Your options could be :
12 drives, single vDev, RaidZ-3
12 drives, single vDev, RaidZ-2 (you can always keep a cold spare to speed up disk replacement when needed)
2x 6 drives RaidZ-2 for more speed but up to 4 drives sacrificed for redundancy.

These 3 options look like your best bet.
Oct 10, 2016
For twelve disks go for two RaidZ2 pools, with 11 opt for one RaidZ3 pool. You may find (older) performance layout guidelines which are mostly moot nowadays.
For Plex streaming you will be fine with read performance of one pool, whereas two pools obviously provides higher random I/O and write performance. Also 2xRaidZ2 will allow you to grow one pool at a time by "merely" replacing/resilvering 6 disks - I started out with 12 3TB disks which has gradually been replaced now having 8TB disks in one pool. As one of the 3TB disks started giving SMART errors that was replaced with 8TB as well.