Strategy for expanding drive

[richardb]

Evening all, I am building a new FreeNAS 11 server. I've got it up and running with 2 8TB mirrored drives and it's all running all tickety boo. It's getting kind of full, though: nearly 88% full. So I want to add some extra drives. I've picked up four 4TB drives and have the bays and controller space to install them.

What I am not sure about is the best way to add them. Should I build them as a RAIDZ1 set on their own, or is there a better way to create a combined set.

My main objective is survivability: this is a media server, so data access speed isn't that much of a deal.

Any thoughts?

 

[m0nkey_]

If you combine them in your existing pool, it's going to become unbalanced and may affect performance. You're better off creating a second independent pool.

If you wish to expand your current, I suggest added a second pair of 8TB drives to expand it.

 

[richardb]

Thanks for the quick response! Well, I have the 4TB drives, so I would like to use them. I'll add them as an independent pool, then see about adding two more 8TB drives when finances permit.

 

[richardb]

Okay, still getting my brain around some of the terminology here. So I have 4 of the 4TB drives that I want to create as a separate pool. Do I need to create a seperate volume as well, or can I add that pool to the existing volume?

When I look at adding the 4 drives to the volume in the volume manager, it offers me options for mirror, stripe, log and cache. I'd like to do this as a ZRaid 1 pool to maximize the space. But it doesn't offer that. Do I need to do that manually in the shell?

 

[richardb]

I needed to get going on this, so I went into the shell and created a new raidz pool, then imported this as a new volume. I would have preferred to incorporate this into the existing volume, but wasn't quite sure how to do that.

 

[danb35]

separate pool. Do I need to create a seperate volume as well

A volume is a pool. But I'd disagree with @m0nkey_'s recommendation, and instead add your new disks to the existing pool. Add them as two mirrored pairs; you can (if you like) replace them with larger disks later.

 

[danb35]

so I went into the shell and created a new raidz pool

That was almost certainly the wrong answer.

I would have preferred to incorporate this into the existing volume

Use the Volume Manager, select your existing pool as "volume to extend".

 

[richardb]

Heh, so I guess it is more complicated than a yes/no ;-). I can do that: I've just created the pool and haven't started using that yet.

I'm not overly bothered about speed, but the unbalanced comment that m0nkey made concerned me: is he not correct? I don't want to introduce problems down the line.

I do want to replace these drives in the near future. So, if I add them as 2x2x4TB mirrored drives, how would I replace them? Would I do that individually, or in pairs? I'm thinking that I would do it individually, wait for the drive to silver, then do the other half of the mirrored pair.

 

[danb35]

I'm thinking that I would do it individually, wait for the drive to silver, then do the other half of the mirrored pair.

Correct.

the unbalanced comment that m0nkey made concerned me: is he not correct?

I won't say he's incorrect, necessarily, but you can see that I'm running with an unbalanced pool (and have been for at least a few years), and don't appear to be having problems.

 

[richardb]

Okay, fair enough. I'll try it out shortly and blame you if it explodes ;)

 

[danb35]

I would recommend, though, keeping the same type of vdevs in your pool. If you currently have one mirrored pair of 8 TB disks, expand the pool with additional mirrored pairs. ZFS will happily accept other configurations (i.e., you could add your four 4 TB disks in RAIDZ1 to that pool), but the more uniform the pool is, in general, the better.

 

[Stux]

And remember, you can't remove a vdev from a pool. EVER.