4x14gb: raid 10 or raidz2

Please give me your Opinion and why?

If this was my “main” system, I’d do raidz2 for the drop of extra safety.

But in reality, I now use mirrors pretty much no matter what for easier expansion (of more space and speed), along with a good backup host.


The problem is that i have 7Tb of data to migrate and raidz2 can be expaded

It’s considerably easier to expand a pool of mirrors than a single RAIDz2 vdev.

zpool add poolname mirror /dev/newdisk0 /dev/newdisk1 and boom, you just expanded your pool of mirrors with two new drives configured as a new mirror vdev.

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I prefer mirrors as well. Easily expandable as @mercenary_sysadmin said and also each mirror you add to expand can be different sizes over time, The only time I think about using Z2 or higher these days is when I’m forced to save money and if I can’t make up the cost difference some where else. But will all things opinion - “your mileage may vary, not available in all regions, taste good, costs less and lasts a long time”

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For me, Z2 primarily becomes interesting once you hit 24 drives or more. At that point, you can split them up into enough vdevs to keep decent IOPS, while sticking with Z2 for the greater fault tolerance and storage efficiency.

Also, 24+ drives heavily implies that you’re operating on enough budget that you aren’t going to get desperate about how to add more capacity RIGHT NOW as cheaply as possible, in as few bays as possible, etc. If you can afford to build a 24+ drive system, hopefully you’re planning things out, keeping enough margin in your operating budget to cope with expansion and replacements easily, etc.

The available netto size is 2x14 GB in both scenarios. RAIDZ2 is slightly better in redundancy.

But the main competitive advantage of RAID10 is the speed. Some years ago when I built my PC I tested both scenarios with 4 x 4 TB WD drives. RAID10 outperformance RAIDZ2 significantly. I am doing frequent performance tests with fio and the results I am getting for the RAID10 are, from my point of view, spectacular: read speed is between 300-350 MB/s and write speed is 200-250 MB/s with 8 fio jobs of 8 GB size each (the PC has 64 GB RAM). RAID10 benefits significantly from parallel reads and writes. RAIDZ2 is by far not that fast.

If your use case is a backup system with data at rest, performance is not your main concern and I would pick RAIDZ2 for the better redundancy.

But if your use case is daily operation on the ZFS pool, with users doing file operations during their daily business, I would always go for RAID10.

Sorry for the late reply, but I just joined this forum.

I agree totally with you.

I don’t have a backup system and performances are not mandatory. Raidz2 (already done)