Should I mirror my SSDs

[microbug]

In preparation for FreeNAS 10's VMs, I'm planning to get a small ~120GB SSD (or two) to put them on. Are consumer SSDs reliable enough to just have one under ZFS? I will be doing backups of course. Ideally I'd like to avoid having two SSDs as I'm a little pushed for SATA ports (6 on the mobo, I'd like to use 5 when I upgrade my HDD array though I could probably manage with 4. Mini ITX board so only 1 PCI-E slot.)

 

[JohnDigital]

I vote yes.

 

[darkwarrior]

Hi there,
mirror them, definitely. ;)
Like this ZFS will be able to rebuild blocks from the other disk, should some blocks fail (and they will... at some point) :p

 

[Robert Trevellyan]

I'm a little pushed for SATA ports

In this context, I say, don't bother, just make sure you always have an up-to-date backup of your configuration.

 

[microbug]

I've been thinking about this and have decided to buy a large SSD (500GB) to store VMs, some user files and various application caches on, and copy it nightly to the (redundant) HDD array, keeping snapshots of it there for a few weeks. That way, if ZFS detects a checksum error I can just restore from a recent snapshot.

 

[Robert Trevellyan]

I take back what I said, for some reason I thought you were referring to the boot device.

Your plan to backup a single-SSD pool to your main pool makes sense, but you'll have to shut down the VMs before each backup. Otherwise, you're likely to have trouble restoring them intact, since their internal filesystems may not be in a consistent state.

 

[microbug]

Hmm, good point. I suppose it doesn't matter too much as I'll run the backup in the middle of the night so the disruption will be minimal.

 

[darkwarrior]

The matter is not just a disruption ...
What @Robert Trevellyan points out, is the fact that you will have inconsistent potentially broken/ unbootable VM backups...
Therefore you will not be able to be 100% sure of the backup, unless you power-off the VMs, run the backups and restart the VMs... ;)

 

[microbug]

Sorry, I did mean that I would have to shut down the VMs first ('the disruption').

 

[darkwarrior]

Oups, my bad. All is good then :D