Noob here. Recommended setup for four 2TB drives?

[joeboxer]

Will be used for streaming movies on a home network and photo and document backup. The plan is to have only Windows and applications (on SSDs) in all home computers, and all documents and videos will be stored on the network.

I have 4 2TB drives. Two are brand new and blank two already have data on it (maybe maybe I can empty one onto various other drives I have lying around, so then I would have 3 free drives and 1 used drive) so I assume I can't set up the entire network in its optimal state, but rather set it up with a subset of the drives, and then put some of my data on the volume, and then add the other one or two disks to the volume.

What would be y'all's recommendation? I am thinking either 2x2 mirror (which would give me 4TB total), or I am wondering if a RAID-Z2 would be appropriate for my needs (and if it makes sense to buy a fifth disk, I would consider that as well). But can I set up a RAID-Z2 with only 2 drives to start, and then add the other two?

Thanks guys!

 

[joeschmuck]

You need all the drives available when you establish your pool (RAIDZ). I think there is one exception, don't recall it well but I think it might be if you add a mirror to a single drive?

I think you need to determine how important the data is that you plan to store of the drives to know if you need a RAIDZ1 or RAIDZ2. If this is just streaming movies then to me a RAIDZ1 would be fine as you can tolerate a single drive failure, replace the failed drive and no data loss. In my opinion a RAIDZ2 or Z3 would be for critical "I cannot lose this data ever" situation. For me that means I would back it up to a CD/DVD if it were that important.

Again, you need to know how much storage space you think you will desire. Four 2TB drives in a RAIDZ1 will give you ~6GB of storage. That is what I'd recommend.

If you have any data on the drives before you start, save off the data if you want to keep it!

 

[joeboxer]

Thanks. I think I might stick with mirror, because I only need to upgrade in sets of two instead of an entire vdev of 3 or 4, plus (as I understand it) it has a fault tolerance that is better than Z1 and worse than Z2, which is fine for my needs, and it has better read performance than either Z1 or Z2. (I am basing this on http://constantin.glez.de/blog/2010/01/home-server-raid-greed-and-why-mirroring-still-best)

 

[ben]

joeboxer, that's correct. In your situation I would definitely go with mirrored pairs for the better performance. just remember that if a mirror pair fails, data on both mirrors is lost (if they're striped in RAID 10).

 

[joeboxer]

Is RAID 10 how ZFS stripes mirrors? I set it up with ZFS - mirror.

 

[ben]

If you put more than one mirror (or any other kind of group) under one top-level pool it will stripe them together much like RAID 10, with the characteristic that the whole pool depends on each RAID group within it.