[SOLVED] Adding drive to mirror

[Brtrnd]

Hi
I'm moving from synology to proxmox; so to start I migrated 1HDD to proxmox, set everything up.
Now I'd like to move my second drive to proxmox, and both should be mirrors of eachother. So I'm not expanding as I find in most guides.
SDA is the new empty disk, SDB is currently the disk in the zpool with all of my data.
I think I only need these two commands:

• add disk : zpool attach tank /dev/sdb /dev/sda
• check data: zpool scrub tank

I'd like to ask if I'm correct in doing this? I wouldn't want my empty drive to be mirrored to the full drive.
Is there a way i can destroy my existing data? what would be a good safeguard against this?

Thank you

For reference:

root@***:~# zpool status
  pool: tank
 state: ONLINE
  scan: scrub repaired 0B in 04:53:36 with 0 errors on Sun Jan 11 05:17:37 2026
config:

        NAME        STATE     READ WRITE CKSUM
        tank        ONLINE       0     0     0
          sdb       ONLINE       0     0     0

errors: No known data errors

 

[Impact]

I don't do that often but that looks correct to me and the second command shouldn't be needed. ZFS should be smart enough to know which disk is already part of the pool

 

[UdoB]

In doubt of the details look into the good ol' man page:

man zpool-attach

SYNOPSIS
       zpool attach [-fsw] [-o property=value] pool device new_device
...
       If  the  existing  device is a mirror or plain device (e.g. specified as "sda" or "mirror-7"), the new device will be mirrored with 
       the existing device, a resilver will be initiated, and the new device will contribute to additional redundancy once
       the resilver completes.
...

 

[SteveITS]

I suggest using the device ID instead of the letters.

 

[Brtrnd]

thanks all, did it and it works.