Expanding zpool?

[TeeJayHoward]

Learning about ZFS, so be gentle!

Right now I've got 10 320GB drives in (software) raid-5 backed up onto 3 1TB drives. The ultra-important stuff's also on a couple DVDs at my folk's house. (Offsite backup FTW!) I'm considering going to 15 1TB drives for now, and possibly adding 3-5TB drives in the future, and was wondering if it might not be time to switch over to ZFS and RAID-Z.

I would be adding approximately 6TB of data to my existing 3TB. In the far future, I might add another 30TB or so to it. I'd really like to be able to expand the raid array with a single disk when needed, instead of ensuring my backups are up to date, blowing away the old array, installing matching disks, then copying information over to the new array, blowing away my backups, and installing new disks there too. It'd be a lot nicer if I could just add a 1TB disk to both main and backups, integrate it into the pool, and go.

I understand that you can do a "zpool add raidz <device1> <device2>" to add multiple disks to the existing pool, but doesn't this waste a whole disk as parity? My pockets aren't so deep as to allow for that. I could also force zfs to add a disk to the pool instead of a raid, but if the disk failed, I'm waiting an hour or two for it to restore from backup vs just popping in a new disk... Pain in my ass. Is there some in-between I'm missing? Can ZFS/Raidz utilize the extra space on a newer disk? For example, could I pull a 320GB out, install a 1TB, and utilize the additional space? Or am I stuck only using 320GB of the 1TB drive?

Sorry if I'm rambling a bit, I'm just trying to figure out what I need/want to do.

 

[ChrisBenn]

you have to add a "vdev" at a time, v dev basically being a virtualized disk

it can be a:

1) Single disk - if you do this you loose guaruanteed protection for everything in your zpool - don't
2) Mirror - basically a raid-1 of as many disks as you want
3) Raid-Zx (where x is the number of parity drives).

You get your redundancy/protection from the type of vdev you add to the zpool.

So you can't really add 1 disk at a time - at least you don't want to. What you will probably end up wanting to do is making each of your vdev's a Raid-Z1 (so one disk lost to parity), and add new vdevs either in groups of 3 or 5 (the latter being more effecient, but also costing more).

So you can't add 1 disk at a time when you want to expand (well, you don't want to), but you can expand as you go still - you just have to add 3 or 5 (<- not the only limits, just my guess based on the use case you describe) at a time.

Also I wouldn't bother buyin 1TB drives now. 2TB drives are the sweet spot in pricing right now.