I recently received a critical alert email from my FreeNAS box with the following error:
Device: /dev/ada3, Self-Test Log error count increased from 0 to 1
Device: /dev/ada3, 1 Currently unreadable (pending) sectors
Rather glad to know the email alerts I setup is working reliably, but looks as though I might have a few bad sectors on one of my drives.
The following commands resolved the error without resulting in any downtime.
The drive in question was /dev/ada3, so first login to a shell on your FreeNAS box as root and run a SMART long self-test (Replace adaX with your corresponding device).
1 | smartctl -t long /dev/adaX |
After the test has finished (It might take a few hours) view the results.
1 | smartctl -a /dev/adaX |
From the results remember the sector size and the location of the faulty sector (LBA_of_first_error).
In my case my sector size was 512 and LBA_of_first_error was 3082982872.
To correct the SMART error we will zero out the bad sector(s) on the drive, but first we need to permit access to drive.
1 | sysctl kern.geom.debugflags=16 |
Now zero the sector stated in self-test results out.
Replace of=/dev/adaX, bs=512, seek=3082982872 with values relevant to your drive.
1 | dd if=/dev/zero of=/dev/ada3 bs=512 count=1 seek=3082982872 |
Re-run the SMART report command to check if the ‘Current_Pending_Sector’ is now showing 0.
1 | smartctl -a /dev/adaX |
To check the ZFS file system integrity run a scrub of the pool, replace poolX with the pool name the drive is under (list pools with ‘zpool list’).
1 | zpool scrub poolX |
Finally check the output of the scrub to ensure there are no known data errors.
1 | zpool status -v poolX |
