If you have redundancy, one or two bad sectors can be fixed even without any downtime.
The error message might look something like this:
10-06-2014 16:25:20 Daemon.Critical storage2 Oct 6 16:25:21 smartd[1560]: Device: /dev/ada2, 2 Currently unreadable (pending) sectors
You can see that the faulty device is /dev/ada2. Now, login to console and run long SMART test:
smartctl -t long /dev/ada2
It should tell you that the test is started and when it will finish. After it finishes, check test results:
smartctl -a /dev/ada2
The output will tell you two important things. In information section there is sector size:
Sector Size: 512 bytes logical/physical
Near the end there is SMART Self-test log which tells you whether it failed and what’s the faulty sector number (LBA_of_first_error column)
# 1 Extended offline Completed: read failure 90% 25166 892134344
Now we have all the info we need to fix it. We will directly write to this sector to force it to reallocate. The important parameters are ‘of’ which is your faulty device name, ‘bs’ which is sector size and ‘seek’ which is sector number.
sysctl kern.geom.debugflags=16 dd if=/dev/zero of=/dev/ada2 bs=892134344 count=1 seek= conv=noerror,sync
Then check if the ‘Current_Pending_Sector’ in ‘SMART Attributes Data Structure’ table went to 0:
smartctl -a /dev/ada2
If not, repeat the long test and write to all sectors until they reallocate. Then run a scrub, replace ‘poolname’ with your poolname:
zpool scrub poolname
Finally check scrub status
zpool status -v poolname
That should do it.
dekoder 