Advice on storage pool setup?

[TehCrucible]

Hi all, have been scouring these forums all day to get my head around FreeNAS and I've found some really great info. I'm just about convinced myself to sacrifice this weekend and spend some time getting everything sorted but I'll admit, theres still a few things I'm a little confused about so I thought I'd get my feet wet and ask for help. My apoliges if my questions have already been answered, I'm just looking for some general clarification/advice specific to my setup.

Quick background: I'm looking to migrate from WHS 2011. Running on an Intel i3 dual-core, gigabyte board (h55) chipset, 4gb ram, 8x seagate 1tb drives, in a fractal R3 case (brilliant case btw!). Mainly used for media/file storage and network backups. I'm mostly after performance and redundancy, not as concerned with capacity.

First question(s) is in relation to the setup of my Z-Pool. At the moment im leaning towards using all 8 drives in a raidz2 config. Is there any performance advantage in splitting that into two raidz1 setups under the same pool? Would either setup have an advantage when Im looking to upgrade drive size capacity in the future? I also have a 60GB SSD avail and I have read I can use this as a cache drive? How would this factor into my drive setup?

Second question: Is 4GB RAM enough for my storage capacity?

I'm sure I'm missing something else but I cant seem to remember right now. Anyway, thanks in advance to anyone who as the time to help. =)

 

[jgreco]

The difference between RAIDZ1 and RAIDZ2 is a matter of redundancy; there is no general advantage to having two RAIDZ1 vdevs in the same pool - for this sort of config, at least. You are only able to tolerate the loss of one drive within a Z1 vdev (and potentially up to two within the entire pool, as long as they come from different vdevs). In a RAIDZ2 with 8 1TB drives, you end up with the same 6TB usable space, but you are able to lose up to two arbitrarily selected drives.

In a setup where you were specifying something like "copies=2", however, the two Z1 vdev situation tends to be a winner - each vdev gets a copy of the data, and you can theoretically tolerate the loss of one entire vdev AND a drive from the other one without data loss. I don't believe they ever got around to making sure ZFS guarantees the storage allocated for copies is actually on separate vdev's, but it is still fairly resilient. But this isn't likely to be something you'll be doing or needing.

As far as performance goes, there are upsides and downsides to various configurations, but the best advice is just to try some setups.

4GB is tight; the way FreeNAS is currently configured, it is kind-of optimized for 8GB (or more). That said, 4GB has been made to work by many users, particularly if you read the forums a bit and follow some tweaks. We're running a FreeNAS ZFS box here as an iSCSI datastore, 240GB SSD's mirrored in ZFS as an extent. Works great. Even though it's a bit dodgy, it is a great example of the typical advice being something to take with a little salt.

 

[TehCrucible]

Thanks for the advice mate. Took the plunge. All is going well so far. :)