If you have MPIO (Multipath IO) enabled, the drive failure replacement procedure is slightly different. Please follow the instructions below in order to correctly swap the MPIO drive.


Disk Failure and Rebuild

Pools normally show green and healthy 
 

After disk fails, Pool shows “DEGRADED” in red

Scroll down to see which disk group(s) have a failed drive

Click disk group TAB under Pool and open the DEGRADED Disk group, blink drive so you can physically locate it to replace it.  After replacing it shows (failed or removed)

Navigate to System Settings > MPIO and locate the failed drive you just removed, in the list its text will now be red and it will say "Missing" instead of "OK" under Status. After locating the Missing drive click on the icon to the right of the Status and remove the Missing drive by clicking "Remove MPIO device"

Once the drive has been removed scroll down to the bottom to "Avaliable disks" and select the replacement drive than click "Create MPIO devices from selected". If two drives show up under "Available disks", the replacement should be the one that doesn't have a "dm" for its name, if you are still unsure you can check the Disk Details and confirm based on the Serial Number of the failed drive you removed.After the replacement disk has been added to MPIO, go back to the Storage screen and follow the rest of the instructions to start the resilver process.


If rebuild of new disk doesn’t happen automatically you can click the “Pencil” to the right and Replace


If you have multiple drive sizes ensure you are replacing with the same size disk and hit APPLY

Resilver (ZFS rebuild) will re-establish parity as defined by the disk group.  Ensure that the Pool is back to healthy after the resilvering: 

The event log will show these typical messages for disk failures