Hi Kern,
> It appears that the OS tape driver does not properly
> implement back space record after an EOT. This is a defect of the operating
> system driver, but it is not fatal for Bacula.
>
> You will very likely see this defect show up when Bacula fills a tape and
> writes the final EOT mark then tries to verify that the last block was written
> correctly. Due to the OS driver defect this will fail, but it is only a check
> and your data may still be good. The results from btape re-reading what was
> written does not look encouraging, and it may indicate that the last block is
> not properly written. I personally would be worried.
Indeed I was seeing the same failure to backspace over EOT error in the job
logs:
End of Volume "GSA784L6" at 3910:8005 on device "drive-1-tapestore1"
(/dev/rmt/1mbn). Write of 64512 bytes got 0.
Error: Backspace record at EOT failed. ERR=I/O error
End of medium on Volume "GSA784L6" Bytes=3,909,704,343,552 Blocks=60,604,295 at
28-Mar-2014 21:28
> This can happen if you are not running the tape drive in the right mode
> -- since I have not looked at the Solaris tape drive naming conventions for
> about 8 years now, I forget. I suggest that you verify that using
> /dev/rmt/0mbn
> is what is recommended in the manual.
Rechecked the manual for this. I think 0mbn would have been an acceptable mode.
m=medium density (I've since removed this to let the tape run at its highest
density and am retesting now).
b=BSD-compatible (Needed by Bacula)
n=non-rewind (Wanted by Bacula)
> If you can really do multi-volume restores correctly and you have verified
> that every byte is correct then you are probably OK.
I've successfully restored 3 jobs that were written in the same way. All three
were bpipe backups of zfs streams so I'm fairly confident the restore is
byte-perfect, or the zfs recv would have bailed out. I've updated the config
with "Backward Space Record = no" to disable this check.
Regards,
Ben Roberts
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