ZFS RaidZ1 vs RaidZ2

[Stanri010]

I'm planning a Freenas build with either 5 or 6 4TB hard drives in 1 vdev for z1 or z2 respectively. I know RaidZ2 is slower than RaidZ1 but on average how much slower is it really when you've got 5 or 6 drives? From what I've seen posted, Z1 can be in the 300 to 400 mb/s while Z2 is around 200mb/s? Is this correct? Can having a powerful CPU such as a 4770K bring a Z2 performance close to a Z1? How does Z1 and Z2 perform with small files such as photos or sub 1mb files? Will both file systems be able to saturate a GigE?

Also, I've only got 16gb for the ITX motherboard I'm planning for this NAS. The 1GB per TB of storage suggests that I would need 20GB or 24GB of ram. The issue is that the ITX board only has 2 ram slots and 16GB is the max it can take. 16GB sticks only come as registered ram and is thus incompatible with the system. Is 16GB of ram for a Z2 6x4TB really not enough if I don't go for all the bells and whistles such as duplication and caching? I would really hate to have to use a different motherboard, case and build for the intended NAS.

 

[HoneyBadger]

Hi Stanri (Stanley?)

Regardless of speed, RAIDZ1 would be a poor decision nowadays due to the larger individual drive sizes, and the ability to only sustain a single drive failure. I'd go with a 6-drive RAIDZ2 every time.

Given a powerful enough CPU - a Haswell Pentium, even - the performance should be close to the same. Where RAIDZ doesn't do well is small files, and you're asking about that ... so either one will perform worse than a mirror setup. But with that said, either of them will be perfectly capable of saturating a 1Gbps link over sequential I/O - even the slow machine in my signature can do that, and it has a two-drive mirror.

1GB per TB is really more of a performance guideline. You're above the 8GB minimum, and 16GB should be fine there. Note that you should go with an ECC supported board/CPU/memory.