[Bacula-users] LTO3 tape capacity lower than expected

Hi there,

I'm struggling with my LTO3 autochanger (Quantum Superloader3). We're
using HP tapes of 400/800 GB capacity (uncompressed/compressed).
Everything has been running fine for about 3 years now (OS: OpenSuSE
10.2, package bacula-postgresql-2.2.5-1), but we're starting to really
fill our tapes (we use a one tape per day strategy and they get recycled
before next use).

I did a btape "test" and all worked fine. Then I did btape "fill" which
ended up like this:

4:06:26 Flush block, write EOF
Wrote blk_block=3460000, dev_blk_num=4000 VolBytes=223,211,455,488 rate=30393.7 
KB/s
Wrote blk_block=3465000, dev_blk_num=9000 VolBytes=223,534,015,488 rate=30404.5 
KB/s
Wrote blk_block=3470000, dev_blk_num=14000 VolBytes=223,856,575,488 
rate=30411.2 KB/s
Wrote blk_block=3475000, dev_blk_num=3500 VolBytes=224,179,135,488 rate=30397.2 
KB/s
Wrote blk_block=3480000, dev_blk_num=8500 VolBytes=224,501,695,488 rate=30403.8 
KB/s
wrote blk_block=3485000, dev_blk_num=13500 VolBytes=224,824,255,488 
rate=30414.5 KB/s
05-Jan 14:07 btape JobId 0: End of Volume "TestVolume1" at 327:1 on device 
"Superloader-Drive" (/dev/nst0). Write of 64512 bytes got -1.
05-Jan 14:07 btape JobId 0: Re-read of last block succeeded.
btape: btape.c:2345 Last block at: 326:15500 this_dev_block_num=1
btape: btape.c:2379 End of tape 327:0. VolumeCapacity=224,953,344,000.
Write rate = 30386.8 KB/s
Done writing 0 records ...
Wrote state file last_block_num1=15500 last_block_num2=0


14:07:31 Done filling tape at 327:0. Now beginning re-read of tape ...
05-Jan 14:07 btape JobId 0: 3301 Issuing autochanger "loaded? drive 0" command.
05-Jan 14:07 btape JobId 0: 3302 Autochanger "loaded? drive 0", result is Slot 
1.
05-Jan 14:07 btape JobId 0: 3301 Issuing autochanger "loaded? drive 0" command.
05-Jan 14:07 btape JobId 0: 3302 Autochanger "loaded? drive 0", result is Slot 
1.
05-Jan 14:07 btape JobId 0: Ready to read from volume "TestVolume1" on
device "Superloader-Drive" (/dev/nst0).
Rewinding.
Reading the first 10000 records from 0:0.
10000 records read now at 1:5084
Reposition from 1:5084 to 326:15500
Reading block 15500.
Error reading block: ERR=block.c:1008 Read zero bytes at 326:0 on device 
"Superloader-Drive" (/dev/nst0).


There were no error messages in the system log nor dmesg. So it looks
like my 400 GB tape takes only about 224 GB of data? This number seems
to be different for different tapes, some take 230, some 240, some less.
The autoloader doesn't report any errors either. System load was
negligible.

The device is attached to an

Adaptec AIC79xx driver version: 3.0
Adaptec 39320A Ultra320 SCSI adapter
aic7902: Ultra320 Wide Channel B, SCSI Id=7, PCI-X 101-133Mhz, 512 SCBs
[...]
Target 4 Negotiation Settings
        User: 320.000MB/s transfers (160.000MHz RDSTRM|DT|IU|RTI|QAS,
16bit)
        Goal: 160.000MB/s transfers (80.000MHz DT, 16bit)
        Curr: 160.000MB/s transfers (80.000MHz DT, 16bit)
        Channel A Target 4 Lun 0 Settings
                Commands Queued 56783788
                Commands Active 0
                Command Openings 1
                Max Tagged Openings 0
                Device Queue Frozen Count 0
        Channel A Target 4 Lun 1 Settings
                Commands Queued 1234
                Commands Active 0
                Command Openings 1
                Max Tagged Openings 0
                Device Queue Frozen Count 0

When I tried to write the original label back to the tape, I got:

05-Jan 14:57 btape: Fatal Error at dev.c:1651 because:
dev.c:1650 Attempt to WEOF on non-appendable Volume
05-Jan 14:57 btape JobId 0: 3301 Issuing autochanger "loaded? drive 0" command.
05-Jan 14:57 btape JobId 0: 3302 Autochanger "loaded? drive 0", result is Slot 
1.
Wrote Volume label for volume "TestVolume1".

Any hints what might be wrong here? Anything I could test?

Thanks!

Tino.

-- 
"What we nourish flourishes." - "Was wir nähren erblüht."

www.lichtkreis-chemnitz.de
www.tisc.de

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