Grow ZFS Pool

[night_rider]

I looked for the version of ZFS that FreeNAS 8 is built on but did not see it. I know it's a newer version than 7. Does it allow you to add new drives to the pool? Does ZFS yet allow this in any version?

I think I've resolved all the issues I've had with FreeNAS and am ready to wipe out my test pool, create a new pool and move my data over to begin using it. I want the server to have some legs though. I probably have 2Tb of media to move to it now.

My current pool is (2) 1.5 Tb Samsung F3 drives and (2) 2 Tb Samsung F3 drives. This gives me 4.4 Tb in RaidZ. It's mainly a media server on my home network as well as a Time Machine backup.

If I still cannot add drives to ZFS I was considering :

a. adding another drive or two (2Tb Samsung F4) and a SiL raid card
b. partitioning the drives for up to 8 partitions for later pool growth

I'd appreciate any thoughts and insights.

 

[freeflow]

ZFS has always allowed disks to be added to pools. What it does not allow is adding a disk to a raidz to take it from 4 to 5 disks for example. If you have a pool with a raidz of 3 disks then you can easily add another 3 disk raidz to the pool and still have a single mountpoint for the pool.

Whether you can add disks to a pool under the FreeNAS 8 GUI is a different question.

Rather then two new 2TB disks you might consider 5x1TB. This would give you a raidz1 with 4TB usable space. It also means that your data disks are a power of 2. There have been some posts recently that suggest for zfs raid that data disks should be a power of 2 in number (2,4, 8 etc) plus what ever parity disks are needed for your flavour of raid.

If you are planning on destroying your pool anyway, then you could also consider deliberately degrading your raid by removing your 2x2TB, low level formatting them to remove partition info, building a raidz with 3 new 2tb disks (5x2TB in total). This would be an 'interesting' way of moving your data to a new raidz.

Have fun!!

 

[matthewowen01]

this is all wrong. the version of zfs that FreeNAS uses does not support the auto expand flag

 

[night_rider]

@freeflow, @matthewowen01 Thank you for your thoughtful replies.

You confirm that I cannot add disks to my raidz. I do hope this is a limitation of ZFS that is lifted in the future.

I think for the time being I will spring for one more 2Tb drive and build my raidz with 1.5, 1.5, 2, 2, 2Tb creating a 6.2 Tb raidz. This should last me for awhile. In the long term I could swap out the 1.5Tb drives if 3 or 4Tb drives come down in price. I was hesitant about a partitioning scheme to build more devices for the pool.

Price is a consideration. I'm notoriously cheap. Raidz2 is ideal but just a bit more expensive and it's just media. The same for adding another raidz as I end up paying for redundant drives again.

Thanks again for your insights.

 

[matthewowen01]

you're very welcome. if you are planning on going with a raidz with 6 drives, i would highly recommend you buy them from different places so they come from different batches.

i had a mirror of 2, 2TB drives, both drives failed within 4 hours of each other. i no longer use raidz, i now always have 2 disks of redundancy just in case, granted i lost 9 TB to redundancy across all my pools.

 

[esamett]

or spread out the purchases over several weeks.

 

[cypher1024]

You confirm that I cannot add disks to my raidz.

While it's true that you currently cannot add extra disks to a vdev, you can add extra vdevs to a pool. Strictly speaking, all vdevs should be identical for optimal performance, but ZFS will deal with mismatched vdevs just fine. The only thing you have to be careful about is mismatching replication levels. If you add a two-disk stripe to a pool and one of those disks dies, you lose the whole pool.

I think for the time being I will spring for one more 2Tb drive and build my raidz with 1.5, 1.5, 2, 2, 2Tb creating a 6.2 Tb raidz.

I'm not sure that your figure is correct. From what I understand, you're going to use five disks (2 x 1.5TB & 3 x 2TB) in RAIDZ (i.e. single redundancy). When you mismatch sizes, all disks are treated as if they are the same size as the smallest disk. So effectively you have 4 x 1.5TB drives (because you lose one drive worth of space to parity data). I find that I get about 0.89TiB of usable space for each 1TB worth of disk.

That yields about 5.34TiB of usable space. If you upgrade the 1.5TB drives to 3 or 4TB items in the future, you'll get about 7.12TiB of usable space.

or spread out the purchases over several weeks.

Ideally you should also introduce the new disks one-by-one whenever possible. As matthewowen01 experienced, sometimes drives will fail after a very specific amount of time. This is not good when your rebuild time is many hours. You can seriously reduce this risk by introducing new disks as far apart as possible so that their time online isn't identical.