Intro
When a disk gets older, there may be some bad sectors on it. In fact every disk has bad sectors. They are just marked as bad and not used by the disk. Every disk has spare sectors to use if some will fail and the disk will remap the corrupted parts to the good ones as soon as we try to write to a bad sector. So this is how we can trigger the remap by hand.
Even if this fix works, consider replacing the failing disk. It may still be ok for a long time bud then suddendly fail in a moment of Murphy’s law. If the disk is brand new, send it back for a warranty replacement.
Locate the start LBA value of the bad area
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smartctl -t long /dev/ada2
smartctl -a /dev/ada2Set debugmode to overwrite the sectors
sysctl kern.geom.debugflags=16
Overrite some sectors
I usually overwrite not just one sector because in my cases I allways had multiple corrupted sectors near the same position! Again: Backup your data!!!
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dd if=/dev/zero of=/dev/ada2 bs=512 count=10000 seek=<startsector> conv=noerror,sync
sysctl kern.geom.debugflags=0
start a scrub to restore the data
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zpool scrub poolname
zpool status -v poolname