Is there a performance difference/advantage between these two setups?

[tethlah]

I'm about to build my server out, originally I was going to do a raidz2 with 6 drives, and later expand my zpool with another raidz2 with 6 drives.

So here is the question, I might be able to get a great deal on some wholesale drives, in which point I'll go ahead and buy 12 drive all at once. So the obvious space differences, are there performance differences or any other advantage to one set up over the other?

Setup 1: Zpool(6 drive RaidZ2 + 6 drive RaidZ2)
Setup 2: 12 drive RaidZ3

Like I said, I know the space differences so it's not even a factor or needs to be remotely considered in the discussion. I just want to know about performance, safety of data, etc between the two.

 

[HoneyBadger]

Performance: The dual RAIDZ2 should be faster, as it will have two vdevs to stripe across versus the single RAIDZ3. Sequential I/O might be slightly higher on the RAIDZ3 setup as you'd have 9 data drives, but unless you have 10GbE and are feeding it exclusively sequential I/O I would prefer the 2x Z2 here.

Redundancy: Dual RAIDZ2 setup will allow you to lose up to 4 drives, but only two per vdev. Single RAIDZ3 will allow you to lose any three. So the Z2 could fail sooner (if you allow three failures in a vdev) but conversely might survive longer (if you lose two from each).

My choice would be 2x RAIDZ2. Make sure you give them a good burn-in period especially if you're buying 12 at once from a wholesaler, you want to identify any early failures out of the gate.

 

[depasseg]

2 RAIDZ2 pools will have the theoretical bandwidth of 8 drives and the IOPS of 2 drives
1 RAID Z3 pool will have the theoretical bandwidth of 9 drives and the IOPS of 1 drive.

I'd go with 2 RAIDZ2's.

 

[Robert Trevellyan]

Setup 1: Zpool(6 drive RaidZ2 + 6 drive RaidZ2)

With this setup, if you want to expand capacity by replacing drives, you only have to replace 6 drives.