On 18/08/2016 00:59, Tim Small wrote:
Hello,
I have had a look around at the other md arrays I manage following the
problems I've recently written about...
I have a machine with a single local SATA disk (an old laptop which only
has capacity for a single disk, and is used for backups), and a remote
iSCSI disk. Both devices are members of a RAID1, with the remote drive
having the write-mostly flag set.
The iSCSI device had a write error during a resync, due to a transient
memory allocation failure on the remote machine.
I've cleared the write_error and want_replacement flags for the device
according to the kernel md docs, but can't see how to provoke md into
attempting to scrub the bad blocks?
Also in general, are there any mechanisms to get md to retry for longer?
I've done this so-far:
ISCSIDISK=$(basename `readlink
/dev/disk/by-id/wwn-0x60014059ba55d40d7fc416d928211f5b`)
echo 600 > /sys/block/${ISCSIDISK}/device/timeout
in an attempt to work-around transient write errors due to memory
allocation failures, target machine reboots, network errors etc.
Should I be doing anything else (e.g. can I configure retries for failed
writes)?
In the past I've done this with NBD and eNBD (Network Block Device and
Enhanced...), both worked really well. Any remote error/problem meant
that the remote disk was failed, and fixing the remote issue, and then
re-add to the array, (with the bitmap enabled) meant a quick resync.
More recently, I use DRBD for the same thing, it seems to be a lot more
reliable, automatic, etc (8.4.x version, the 9.0.x versions is still a
bit experimental in my experience).
So, I can't directly answer your questions, other than to suggest you
consider looking at other technologies that are more directly designed
to do that.
Regards,
Adam
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