Le 18/08/2016 16:59, Simon Hobson a écrit :
OT, but there seem to be a few people who understand such in-depth stuff here
;-)
I'm in the process of recovering (with ddrescue) files of a failing drive - no backups as
"it's only TV" recordings and I can't afford the disk space anyway. It's going
better than I expected with most of the files (typically anything between 1G and 4G in
size) reading without any errors - retries on the disk, but no actual read errors.
Tedious because when the drive warms up, it "goes titsup*" (producing lots of
DID_BAD_TARGET errors) and I have to unplug it and let it cool down before restarting the
recovery process.
But, mounting the source drive read-only doesn't seem to actually mean read-only as I see
errors in syslog related to write errors on the disk. After a dig around, I came across
"blockdev --setro <device>" which as I read things means the device itself
should be set as read-only.
But I still see things like this in syslog (when I unmount the filesystem) :
end_request: I/O error, dev sdf, sector 3037143616
Buffer I/O error on device sdf5, logical block 352878592
lost page write due to I/O error on sdf5
JBD2: Error -5 detected when updating journal superblock for sdf5-8.
Is it me not understanding things, or is it still trying to write to the disk ?
Or is it just that the filesystem code still tries to write, but fails either
because the filesystem is mounted read-only or the device is set read-only ?
* Total Inability To Support Usual Performance
_
Not sure, but could you try to also mount the disk with the noatime
option. I don't know if ro implies noatime.
Didier
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