Replace degraded disk, remove mirror

TrueNAS General
1

Hello I am using TrueNAS-13.0-U6.2 and have a 4 disk mirrored pool. 2 disks are 1TB and the other 2 are 500 gb.
this makes up one pool of 1.5 gb. One of my 1tb disks is degraded and has some read errors.

What I Want to do is replace all of these with one 12TB CMR disk, then eventually when budget allows add another 12tb to mirror.

So for now what is the best way to add the new 12 TB disk and copy all my data to that disk, remove all the other disks and hopefully keep the same pool etc so clients that connect dont have to re-map to the nas or anything?

Hope all this make sense

2

As your pool is mirrors then you can remove vdevs as long as data can be evacuated onto another vdev.

So:

  • Add the new disk as another vdev - single disk stripe
  • Remove the other vdevs, one at a time - this will take some minutes
  • Done
3

Would be best to replace one of the 1TB disks, then remove all the other members and vdevs.

That means only evacuating what’s on the 500GB mirror VDev. Which means less redirected blocks.

BTW, just pointing out your data will be at risk when you have no redundancy in your pool.

1 Like
4

@Stux is right - that would be quicker and more efficient
The only issue is if you run into the bug where pools won’t expand properly (something to do with the way the disks are partitioned). My way will avoid that potential issue

5

No partitioning/extension bug with CORE! This is a SCALE exclusive… :stuck_out_tongue_winking_eye:

6

Thanks seems simple enough would this way copy the data from the current pool to the new Single disk.
Also I cant add another disk before removing one because I only have 4 sata ports and they are all used up. I was hoping I could remove the degraded one then add the new one?
Thoughts?

7

If you add a 12 TB drive as a replacement for the failed one, you’ll end up with a very asymmetrical pool: 12 TB + 1 TB as one mirror and 0.5 TB as another mirror. This setup still only provides 1.5 TB of usable space, and you would need to replace the other three drives to achieve a pool with uniform disk sizes and consistent performance.

It’s better to create a new pool on the 12 TB drive, copy the data over (using a replication task or “zfs send”), and then remove the old pool and drives. Afterward, you can add another 12 TB drive to the new pool.

8

As already explained, the transfer is more easily achieved by first mirrorring the 1 TB drive to the new 12 TB drive (possibly even creating a 3-way mirror with the failing drive), and then removing the 1 TB drive and the other 2*0.5 TB vdev.
The sole benefit of creating a new pool would be to keep the old set of drives as a cold backup.

9

OK and I can remove the degraded drive add the new 12TB drive as a new pool and copy data to it ?
Do I need to do anything to break the 1tb Mirror or will removing the degraded drive do that on its own.

10

As you don’t have a spare SATA port. Remove the degraded drive then add the 12TB in as a mirror to the remaining single drive. Resilver then remove the other vdev

Note for anyone considering TrueNAS. Always have a spare port available.

1 Like
11

Thanks for all the help!