ZFS detects far more errors that traditional filesystems will simply miss.
This means that many of the possible causes for those errors will be
something other than a real bad block on the disk. As Edward said, the disk
firmware should automatically remap real bad blocks, so if ZFS did that
too, we'd not use the remapped block, which is probably fine. For other
errors, there's nothing wrong with the real block on the disk - it's going
to be firmware, driver, cache corruption, or something else, so
blacklisting the block will not solve the issue. Also, with some types of
disk (SSD), block numbers are moved around to achieve wear leveling, so
blacklistinng a block number won't stop you reusing that real block.
--
Andrew Gabriel (from mobile)
------- Original message -------
From: Edward Ned Harvey
<opensolarisisdeadlongliveopensola...@nedharvey.com>
To: didier.reb...@u-bourgogne.fr, zfs-discuss@opensolaris.org
Sent: 8.11.'11, 12:50
From: zfs-discuss-boun...@opensolaris.org [mailto:zfs-discuss-
boun...@opensolaris.org] On Behalf Of Didier Rebeix
from ZFS documentation it appears unclear to me if a "zpool
scrub" will black list any found bad blocks so they won't be used
anymore.
If there are any physically bad blocks, such that the hardware (hard
disk)
will return an error every time that block is used, then the disk should
be
replaced. All disks have a certain amount of error detection/correction
built in, and remap bad blocks internally and secretly behind the scenes,
transparent to the OS. So if there are any blocks regularly reporting
bad
to the OS, then it means there is a growing problem inside the disk.
Offline the disk and replace it.
It is ok to get an occasional cksum error. Say, once a year. Because
the
occasional cksum error will be re-read and as long as the data is correct
the second time, no problem.
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