Raid 5 Mixing Disks

[acortizo]

The question I want to ask is if TrueNAS allows setting up a RAID 5 from:

• 1 disk of 4TB
• 1 disk of 3TB and one of 1TB, making them behave like a RAID 0
• 1 disk of 1TB, one of 1TB, and another of 2TB, making them behave like a RAID 0

Is this approach possible to achieve a RAID 5, assuming that the sums of each set add up to 4TB?
Thank you very much.

 

[Ericloewe]

Simple answer is "no", because the potential for things to go wrong there is pretty significant.

 

[danb35]

First, TrueNAS doesn't to RAID 5. The closest it comes is RAIDZ1, which is ZFS single-parity RAID. Second, no, TrueNAS doesn't support such a configuration. In theory you could do something like this if you were using a hardware RAID controller, setting up each RAID0 array and letting TrueNAS see each as a single disk, but hardware RAID controllers are strongly discouraged with ZFS.

 

[Arwen]

To give some back ground, ZFS was designed for the data center. Thus, it does not support random disk sizes to make complicated environments that people who need to save money want.

The only thing you can do with those disks, that is supportable, is make Mirrors;

• 3TB mirrored to 4TB, temporarily wasting 1TB of the 4TB disk
• 1TB mirrored to 2TB, temporarily wasting 1TB of the 2TB disk
• 1TB mirrored to 1TB

That would give a total raw space of 5TBs in a ZFS pool

Later, if you get another larger disk, (2TB, 4TB or larger), you can replace one of the smaller drives in a mirror that currently wastes space to grow that mirrored part.

One note. Because you list random disks, you need to check if any are SMR, Shingled Magnetic Recording. SMR disks cause problems with ZFS, and are highly discouraged.