This documents the steps to replace a failed drive in a mirror configuration in FreeNAS 11.1-U7. This process is really easy with FreeNAS.
This scenario is in contrast to replacing a failed drive before it fails (in a Centos “ad-hoc” ZFS system).
(Note: at this time, FreeNAS 11.3-U4.1 is available. It has a different GUI from the description below.)
First, confirm FreeNAS agrees that the drive is dead. Your alert in the upper right corner will be showing red “Critical”.
Second, physically replace the drive with an equal-or-larger sized drive.
Third, from the FreeNAS 11 GUI:
- Click “Storage”
- Click on the pool name row (first row, not the second row)
- At the bottom, click “Volume Status”
- Click on the row below the “mirror-0” that says “UNAVAIL”
note: the failed disk will probably have a number, like 11421970349345372421, instead of a device, like ada4p2
after you do this, a “Replace” button appears at the bottom of the screen
- Click on “Replace”
after you do this, a dialog “Replacing disk 11421970349345372421”
The drop-down dialog will be pre-populated with the newly-inserted disk, by device name, like ada5 (X.Y TB)
- Push “Replace Disk”
after you do this, the dialog changes to “Please wait…”
after about 60 seconds, the dialog closes, and returns to your pool status
At this point, all of the disks should show “ONLINE”, and the top status changes to “Resilver”.
Eventually, a “Progress: NN.nn%” will start showing the resilvering status of the drive.
You can also run “zpool status” to see the resilver progress.
Extra tidbit: the 4TB drive resilver (2.7TB used) took 8h35m, which is 91MB/second.