RAIDZ on different sized HDD's

[Benxas]

Apologies if this is a noob question, but I couldn't find the answer on the forums or in the 9.1.1 user guide.

Do all HDD's have to be the same size to create a RAIDZ1 or RAIDZ2 ZFS volume?

I have 2 x 3TB and 2x 1TB and the system (ZFS volume manager) only offers me mirrors for redundant storage. I'm pretty sure with Raid5 and Raid 6 you don't need all the HDD's to be the same size (various commercial nas' seem to manage this fine).

Many thanks in advance for clarifying this.

 

[dlavigne]

The ZFS Volume Manager is designed to prevent users from inadvertantly creating non-optimal pools. Users who are determined to do so can still use the command line to create their pool.

 

[Benxas]

Would it be non-optimal because the pool would only make use of 1TB from each drive as that's the smallest drive size in the pool or are there other reasons?

 

[dlavigne]

Yes, that is part of it.

 

[Benxas]

So unless I have three or four drives of the same size, I'm best to go for two mirrors?

When it talks about making a pool bigger (admittedly it's not recommended) by replacing a drive with a larger one and resilvering the pool, would that work in a RADIZ configuration as well?

 

[warri]

Yes, growing the pool in a RaidZ works fine. To grow the pool you might have to issue one or two commands via the Console, but it's documented in the manual: http://doc.freenas.org/index.php/Volumes#Replacing_Drives_to_Grow_a_ZFS_Pool

 

[brbubba]

It will be 1TB across all drives, but if you eventually get 2x more 3TB drives you can remove each 1TB individually, resilver, and once all are complete it should automatically expand to the full size.

In this case though if you are ok with not having a RAIDZ array you can create two mirrors out of both sets and have them as part of the same pool. ZFS will automatically assign files to each mirror as needed and it will look like one pool to you. This method can also be expanded, i.e., you get 2 X 3TB drives, remove the 1TB one at a time and then resilver each time and by the end the mirror will automatically be 3TB.