> dd test has been run...
>
> Just before the last run, I switched off the compression on the tape...
>
>
> root@backup:~# date; dd if=/dev/zero of=/dev/nst0 bs=1024k count=10240; date
> Mon Jan 12 20:50:35 CET 2009
> 10240+0 records in
> 10240+0 records out
> 10737418240 bytes (11 GB) copied, 88.6869 s, 121 MB/s
> Mon Jan 12 20:52:04 CET 2009
> root@backup:~# date; dd if=/dev/zero of=/dev/nst0 bs=2048k count=10240; date
> Mon Jan 12 20:56:32 CET 2009
> 10240+0 records in
> 10240+0 records out
> 21474836480 bytes (21 GB) copied, 170.224 s, 126 MB/s
> Mon Jan 12 20:59:22 CET 2009
> root@backup:~# mt -f /dev/nst0 rewind
> ^[[Aroot@backup:~# mt -f /dev/nst0 weof
> root@backup:~# date; dd if=/dev/zero of=/dev/nst0 bs=2048k count=82400; date
> Mon Jan 12 22:48:58 CET 2009
> 82400+0 records in
> 82400+0 records out
> 172805324800 bytes (173 GB) copied, 1336.05 s, 129 MB/s
> Mon Jan 12 23:11:14 CET 2009
>
This is normal and the expected result.

>
> # Switched off compression:
>
> mt -f /dev/nst0 compression off
>
>
> root@backup:~# date; dd if=/dev/zero of=/dev/nst0 bs=2048k count=102400;
> date
> Tue Jan 13 07:37:47 CET 2009
> dd: writing `/dev/nst0': No space left on device
> 40406+0 records in
> 40405+0 records out
> 84735426560 bytes (85 GB) copied, 9176.92 s, 9.2 MB/s
> Tue Jan 13 10:10:44 CET 2009
> root@backup:~#
>
>
> Just able to write 85 GB....
>
This looks very much like either a bad tape or a bad tape drive or
dirty heads on the drive. 9.2MB/s is way too slow and the time looks
interesting. I mean this is the normal time to write an entire tape.
Its like the drive is writing the entire tape but just at a very low
density. I am no expert on how LTO writes to tapes but I do know that
previous technology tape drives (DLT I believe) when it had media
errors during writing it would rewrite the the block to the next
position on the tape thus reducing capacity.

I would perform a tape drive cleaning with a cleaning cartridge and
perform the non compressed test again. If you get the same result try
this with a brand new tape.

John

------------------------------------------------------------------------------
This SF.net email is sponsored by:
SourcForge Community
SourceForge wants to tell your story.
http://p.sf.net/sfu/sf-spreadtheword
_______________________________________________
Bacula-users mailing list
Bacula-users AT lists.sourceforge DOT net
https://lists.sourceforge.net/lists/listinfo/bacula-users