Hi all, I need to replace a disk in a pool and was reading the docs: https://docs.unraid.net/unraid-os/manual/storage-management#replace-a-disk-in-a-pool

 

In summary: 

1. Stop the array.
2. Physically detach the disk from your system you wish to remove.
3. Attach the replacement disk (must be equal to or larger than the disk being replaced).
4. Refresh the Unraid webGui when under the Main tab.
5. Select the pool slot that previously was set to the old disk and assign the new disk to the slot.
6. Start the array.
7. If presented with an option to Format the device, click the checkbox and button to do so.

 

Full stop I may be misinterpreting this but it reads like this is to be done while the Unraid server is running. Is this required or can I do the drive swap while the server is powered off? Some drives are inaccessible while the server is running. For example:  

1. Stop the array.
2. Disable auto-start
3. Shut down Unraid
4. Physically detach the disk from your system you wish to remove.
5. Attach the replacement disk (must be equal to or larger than the disk being replaced).
6. Start Unraid
7. Open the Main tab.
8. Select the pool slot that previously was set to the old disk and assign the new disk to the slot.
9. Start the array.
10. If presented with an option to Format the device, click the checkbox and button to do so.

 

Thanks!

Edited June 14, 20233 yr by ronmcmxci

39 minutes ago, ronmcmxci said:

reads like this is to be done while the Unraid server is running.

Definitely not.

While some hardware may work, it's not a universal thing. Hotswap has to be supported by the HBA and the drive cage, so it's safer to power down when unplugging and plugging drives.

 

The only quibble I have with your summary and the original is the last step, I'm not sure why it's there to be honest. Formatting would erase the pool, so don't do that unless you don't need the data on it.

@JorgeB, could you check that to see if I misread something?

Okay that makes much more sense. Just to confirm, I can leave the data on the pool? 

I would make a current backup in case something goes wrong, but yes, theoretically it should keep the data.

Just to confirm, after assigning the new drive in the pool slot for the old drive I should see this? Cache 4 is the drive I'm replacing. 

 

Empty slot after removing old drive:

 

After assigning new drive: 

Assuming that's a redundant btrfs pool you can proceed.

i just upgraded my cache pool from 2x256gb ssds to 2x512gb ssds

 

Here's what I did:

 

1) shut down array

2) pull 1 256gb drive

3) replace with 512gb drive

4) start array

5) unraid detects missing pool disk.  assign new 512gb in its slot

6) start array

7) unraid rebuilds 512gb drive with data from other 256gb drive in pool

 once rebuild is done, shut down server

 

repeat 1-7 for the other drive

 

no issues, no muss, no fuss.  sure it took a bit longer than some other methods, but i didn't need to mess with anything and it "just works"

I'm all set here. Easy with no problems. Thanks all

 

How do I know when the rebuild is done and it's safe to replace the next drive?How do I know when the rebuild is done and it's safe to replace the next drive?

When the pool activity stops, you can also check the syslog.

Sorry to reopen an old thread. But I am going to replace my btrfs pool (2 devices) from 2x 1 TB to 2x 2TB nvme.

After I replaced them one by one with data rebuild. How can I extend the pool size? Or will it be done automatically?

Thanks

Edited December 18, 2025Dec 18 by donativo

2 hours ago, donativo said:

Or will it be done automatically

This once both are replaced (may need to reboot - not sure).

4 hours ago, donativo said:

Or will it be done automatically?

It's automatic after both devices have been replaced.