Can I expand a mirrored pool with larger drives?

TrueNAS General
1

Hi,

Currently I have a pool with 2x 4TB disks, one of which is failing. I’m in the middle of choosing a replacement disk. I was thinking of:

  • Purchasing the failing 4TB disk with a single 12TB disk
  • Resilvering the pool with 1x 4TB & 1x 12TB disk (still utilizing only 4TB of space due to the smaller drive)
  • Replacing the healthy 1x 4TB disk with another 1x 12TB resulting in 2x 12TB drives in the pool

Does that makes sense? Could I have 12TB of space in the pool after changing the both drives, or that’s just not the way it works?

Thanks!

2

How bad is the failing disk? You could add the 12TB disk, have a 3 disk mirror, then when the 12 TB disk is written remove the failing disk. You could even do it all together as a 4 disk mirror if you have both 12TB disks.

Otherwise what you’re suggesting makes sense. My VM array (3 way mirror of SSDs) has gone through 2 rounds of a similar process.

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3

The failing disk have hundreds of checksum errors, so I guess pretty bad. I’m still wondering whether I should just offline it at this stage or keep it going. I’ve replicated the dataset that sits on this pool on another healthy pool anyway, and I’ve done this after I saw that the disk is failing.

4

That’s exactly the way it works, once you click the “expand pool” button. iX broke pool auto-expansion in SCALE and have decided “we meant to do that.”

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On 25.10 I saw my raidz2 pool space automatically grow after replacing a 6tb drive with a 12tb drive. The same should happen as long as you replace the drives directly and not create another another vdev