Adding and Modifying Pools

[paulinventome]

I haven't quite been able to work this out.

I'm testing TrueNAS, not using it yet. I have a 4TB SSD and I will get another one to use as a Mirror but I don't that the second yet. I have created a Pool with just the one SSD to see if it works, and it does. Am I able to modify the pool and add the second as a mirror when it comes in or is it better to hold off and then recreate the pool with both SSDs in place? This pool is a general local media server one, but so it can be on without the spinning disk pool running. Performance over 10gbe seems okay, what I would expect.

Similarly I have 4x16TB pool set as ZRaid2 - when I get more drives can I add them to this pool, or is there a performance penalty for doing this?

Thanks!
Paul

 

[sretalla]

Am I able to modify the pool and add the second as a mirror when it comes in or is it better to hold off and then recreate the pool with both SSDs in place?

It's fine to just attach a disk to an existing one to form a mirror.

I have 4x16TB pool set as ZRaid2 - when I get more drives can I add them to this pool, or is there a performance penalty for doing this?

Not so simple...

RAIDZ doesn't currently have an option for expansion of a VDEV, so you're stuck with the 4 that you currently have in that first VDEV.

You can add an additional VDEV if you wish, but that would mean another 4 (or more) disks.

 

[paulinventome]

It's fine to just attach a disk to an existing one to form a mirror.


Not so simple...

RAIDZ doesn't currently have an option for expansion of a VDEV, so you're stuck with the 4 that you currently have in that first VDEV.

You can add an additional VDEV if you wish, but that would mean another 4 (or more) disks.

Okay, that's some great information

Mirror no problem, great.

So what does another vdev mean in terms of an overall pool? 4 drives gets me 30TB with 2 drive redundancy. If I add another 4 vdev does that mean I get 6 drives with 2 redundancy or two sets of 4 with 2?

It sounds like if I want 6 plus 2 then do I have to create this right at the start? I can't just add in more discs and the NAS rebuilds like a Synology would?

Thanks!
Paul

 

[Etorix]

It sounds like if I want 6 plus 2 then do I have to create this right at the start? I can't just add in more discs and the NAS rebuilds like a Synology would?

Correct. If you want a 6-wide raidz2, you have to create it at 6-wide. Raidz expansion is "in the works", has been so for years, may eventually come, with its caveats and limitations, but will NOT allow to go from raidz1 to raidz2 to raidz3—so, still not Synology-style flexibility.

You can always enlarge a mirror vdev, for added redundancy—or remove drives to slim it.
Raidz is set at creation, and cannot be changed.
You can replace drives with larger ones to increase capacity.
You can always add further vdevs to a pool, to increase capacity (and IOPS). E.g. a pool with a single 4-wide raidz2 can receive a second 4-wide raidz2 ("two sets of 4 with 2"). You are not limited to adding identical vdevs, but the pool is as secure as the least secure vdev overall, so it's best to keep it homogenous.

If all data vdevs in a pool are mirrors, you can also remove vdevs (capacity allowing, since data has to be transferred to the remaining vdevs). Raidz vdevs cannot be removed—full stop.
So when using raidz the only way to modify the geometry of a pool is to backup, destroy the whole pool, recreate and restore.