I currently have 6x3TB in a RAIDZ2, upgrading to 9 HDD, which RAIDZ?

[kschaffner]

I'm having some trouble finding some new information about this topic and I've searched the user-guide which didn't answer me either. I like the idea of getting more space on Z2 rather than Z3 but I also want to make sure I am conforming to best practices in regards to disk to raidz type.

Thanks!

 

[gpsguy]

RAIDZ2 is still acceptable.

Are you aware that you can't add 3 new disks into your current 6 disk RAIDZ2 vdev? You woul need to backup up the data, destroy the pool and rebuild it with the 9 disks.

 

[kschaffner]

Yes. I’m well aware that you can’t add disks to a vdev, that to increase an existing pool you have to add another vdev to an existing zpool. I plan to back everything up and recreate the vdev and pool. My question is purely about 9 disks being in a z2 array as I’ve read a little here and there about it being better to have multiples of 2+2 for z2 specifically for zfs blocks being spread evenly across. My case doesn’t allow for 10 disks sadly and thus want to go with 9.

I’m thinking it will work fine, some posts have mentioned a slight reduction in space vs it being even number of disks in the pool.

 

[Ericloewe]

No, that's not an issue for 99% of workloads when using compression.

 

[kschaffner]

So with compression there isn't an issue running an array that isn't "built in the golden rule". I'm assuming this changes with compression off?

 

[Ericloewe]

Somewhat, but it's still not quite as linear as it might seem at first. Besides, there are few scenarios where compression isn't a good idea.