Growing my FreeNAS. What ZFS level should I use?

[Roveer]

I've had a 8 drive, single volume ZFS2, single dataset system running for the last 2 years. Since it's in a Dell R510 enclosure I had 4 additional slots to fill. I just received 4 additional drives and installed them.

Now I understand that I can't expand the volume, so I've made provisions (FreeNAS is actually my backup server) to store the data that was on my FreeNAS box on a temporary NAS so I can nuke the volume and rebuild a 12 disk version to realize the additional disks.

When I went to create the volume and realized I had a few options. Here's what I've come up with:

How should I be configuring for 2 disk failure and most possible storage. I read somewhere that I shouldn't be going with the RaidZ2 with all the disks in a row options because it's 12 disks in one array. I'm assuming the RaidZ2 options is 2 6 disk arrays? is that 4 disk failure, 2 per array? I'm a little lost here, and 14.54TB out of 24TB (21 actual) was a lot more loss than I was expecting.

Thanks,

Roveer

 

[danb35]

Now I understand that I can't expand the volume

You understand incorrectly; it's always been possible to do this (well, at least as long as FreeNAS has supported ZFS).

I'm assuming the RaidZ2 options is 2 6 disk arrays?

That'd be my vote.

is that 4 disk failure, 2 per array?

Yep.

You don't really want vdevs wider than ~10 disks for performance reasons. And you really don't want RAIDZ1 with disks > 1 TB for data security reasons. If this is a backup server, you could fudge this and go for two RAIDZ1 vdevs rather than RAIDZ2--this would give you another 4 TB (~3.6 TiB) capacity in your pool, but only one disk's redundancy in each vdev.

 

[Basil Hendroff]

If this is a backup server, you could fudge this and go for two RAIDZ1 vdevs rather than RAIDZ2

Interesting you say this. RAIDZ1 is what I adopted for my own backup servers. I'm not so sure it was the right decision anymore as my backup servers also contain my oldest disks, which are the ones most likely to fail first.