Having the same issue with two USB disks: SAMSUNG_SV2042H and
Myson_Century__Inc._USB_Mass_Storage_Device_100.
I did some debugging and this is what I came up with:
When you right-click on a USB drive and choose "Safely remove drive", this is
what happens in the background:
1. Nautilus calls udisks --umount <device file of USB drive>"
2. udisks contact a background-process named "udisks-daemon".
3. udisks-daemon inturn invokes "/usr/lib/udisks/udisks-helper-drive-detach".
4. udisks-helper-drive-detach calls some sg3-utils to synchronize the cache and
stop the device ("sg_ll_sync_cache_10" at line ~184 and "sg_ll_start_stop_unit"
at line ~202 in source file "job-drive-detach.c"). Both of these functions
return an error message.
You can easily reproduce the error messages caused by sg3-utils by
running the sg3-utils manually. In order to reproduce the first error
message ("SYNCHRONIZE CACHE: FAILED: No such file or directory"), run
this command:
sg_sync --verbose <device file of USB drive>
Example: sg_sync --verbose /dev/sdc
This yields the precise error message returned by the sg3 backend:
synchronize cache(10) cdb: 35 00 00 00 00 00 00 00 00 00
synchronize cache(10): Fixed format, current; Sense key: Illegal Request
Additional sense: Invalid field in cdb
bad field in Synchronize cache command
In order to reproduce the second error message ("STOP UNIT: FAILED: No
such file or directory"), run this command:
sg_start --stop --verbose <device file of USB drive>
Example: sg_start --stop --verbose /dev/sdc
Again, this yields a more precise error message than the general "No
such file or directory" as shown by the graphical front-end:
Start stop unit command: 1b 00 00 00 00 00
start stop unit: Fixed format, current; Sense key: Illegal Request
Additional sense: Invalid field in cdb
invalid field in cdb
START STOP UNIT command failed
In conclusion, it looks like the sg3-utils send the wrong commands to
the SCSI layer or wherever these commands go (I am not that much into
low level SCSI programming, my apologies). However, I don't see any
adverse effects from these erroneous commands. Even though the sg3-utils
functions return an error, udisk-daemon properly continues and cleanly
unmounts the USB drive as far as I can tell (it invokes umount, which
should sync the cache anyway). To try this out, I removed the two calls
to the functions "sg_ll_sync_cache_10" and "sg_ll_start_stop_unit" from
the source code of udisks "job-drive-detach.c" and recompiled the thing.
Nautilus stopped whining about the failure of these two functions and
the drives are unmounted perfectly. :-)
I would have attached a patch, but I do not really have a clue about
what these two functions do precisely. In fact, it might have been a bad
thing to remove the function calls from "job-drive-detach.c". I cannot
say, if this may result in loss of data (someone with some SCSI
programming knowledge please explain). Plus, I imagine that for most
users it may actually be useful that these functions are called. So it
would not really be a patch.
--
secure remove of external USB-HDD produces error
https://bugs.launchpad.net/bugs/466575
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