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ZFS - Troubleshooting - Replace a Disk

Check the Pool

Verifing that a disk is bad and that it needs to be replaced.

zpool status

Add a New Disk

Add a new disk.
Optionally remove the old disk.

NOTE: Only remove the old drive at this point if it is a redundant setup.

Replace the Old Device

zpool replace testpool c1t1d0 c2t0d0
zpool offline testpool c1t1d0
zpool remove testpool c1t1d0

NOTE: Here the old device is specified first followed by the new device.

If the pool is a redundant configuration, data will be copied from other good disks to the new disk.
If the pool is not redundant, data will be copied from the old device to the new device.

The old drive should also become detached.

Once that is complete, the old device can be physically removed.

NOTE: If the old disk is already removed from the system and a new device has replaced it with the same device name, the following command can be used instead:

zpool offline testpool sdd
zpool remove testpool sdd
zpool attach -f testpool sdc sdd

Wait For Resilvering to Complete

Before the pool will be back to normal it will need to sync data over to the new disk.

It will remain in a degraded status while the data syncs.
This data syncing process is called resilvering.
It may take a very long time depending on the size of the disks and on how much data is on them.

The status of the resilvering can be checked:

zpool status testpool

Physically Remove the Old Drive

Physically remove the old drive.

If it is hot-swappable then just pull it out.
Otherwise, shutdown the system, before removing the device.

Potential Issues

If the bad disk has already been removed from the system you might not be able to specify it by ID.

If this is the case try specifying it by device name or by GUID:

zdb               # Find GUID.
zdb -l /dev/sda1  # In case the 'zdb' command does not work.
zpool status -g   # Find GUID.
zpool status -L   # Find device name, resolving links.

NOTE: If zdb does not output anything, try specifying the device.

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