Moving to a smaller Pool

TrueNAS General
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I currently have a 22TB pool that only contains about 40GB of data. The chances of it growing much is minuscule. It spans 6 drives (3 VDevs of 2 Mirrored 8TB Drives each). I have a set of 4TB drives, so I want to move it to a single VDev of 2 4TB Drives. This should be more than enough. This will free up 4 drive slots in the case, which can be used for additional drives if I need to expand the other pool (when funds become available) but for now will reduce the heat impact on the machine.

Yes, I understand the risk of using Mirrored drives vs. RaidZ[1-3] and for what I am using these for, mirrored makes the most sense. The files are backed up on Blue-Ray Disks and are also stored offsite, so if I lose both mirrors, I can restore fairly quickly.

Now, I don’t have any more connections connections on my LSI SAS, However I have some spare ones on my other server. So I could connect them over there and transfer as needed.

Question:
What’s the best way to do this?

  • Extra points for pointing me in the direction of step by step instructions rather than just saying “Replication”.
  • Assuming I’d like to keep the same pool name, can I just create any new name for the transfer and then rename?
  • While the servers are the same version of TureNAS Scale (22.12.4.2), they do not have the same users or permissions. Will this cause problems if I move the drives back? (Is this even possible?)

Thanks for your advice.

After “moving the pool”, I plan on going through the upgrades (Yes, I know there will be more than one.) to get the servers up to the latest stable versions.

Thanks In Advance.

2

If you have a recent version of TrueNAS, it will have the ZFS vDev removal feature for Mirrored vDevs. Thus, you can remove 1 x 2 disk 8TB Mirrored vDev and when that is done, remove a second 2 disk 8TB Mirrored vDev.

That will free up disk bays. You can then physically remove 2 x 8TB disks and install the 2 x 4TB disks. Then add the 2 x 4TB disks as a Mirrored vDev to the pool. When that is done, you can remove the last 2 disk 8TB Mirrored vDev.

Complicated, but the server can in theory be up and serving data the entire time. (The “in theory” is based on if you have hot swap disk bays or not…)

Now is that the best thing to do?
Maybe not.

If you need disk bays, then yes, remove a single 2 disk 8TB Mirrored vDev. Use those 2 slots for the 2 disk 4TB Mirrored vDev in the new pool. Last, copy the data over.

While ZFS is not the most flexible file system, volume manger and RAID handler, it does have quite a few tricks.

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