On Wed, Jan 06, 2010 at 02:20:06PM +0100, Tino Schwarze wrote:
> > > > It looks like btape is not happy.
> > > >
> > > > Error reading block: ERR=block.c:1008 Read zero bytes at 326:0 on
> > > > device "Superloader-Drive" (/dev/nst0).
> > > >
> > > > Are your tapes old (still good)? Did you clean the drive? Latest
> > > > Firmware?
> >
> > The drive requested cleaning just yesterday which I did. I'm not sure
> > how old the tape in question really is. I used a dell update utility and
> > it updated the drive to v2181 which seems to be the latest for a
> > half-height SCSI tape drive. 30MB/s seems a bit low to me - it should be
> > able to do 60MB/s per spec. Or is that just theory vs. real world?
> >
> > > I would add are you using LTO3 tapes or LTO2 tapes?
> >
> > They are labelled 400GB/800GB - all of the same kind, so they're
> > definitely LTO3. The autoloader says: "Drive Idle Gen 3 Data" in it's web
> > interface, so yes, I'm sure.
> >
> > I could check a very new tape tomorrow or try a shiny new one, just to
> > be sure.
>
> Here are the results for a shiny new tape with block size 512k:
>
> > Wrote blk_block=750000, dev_blk_num=651 VolBytes=391,110,459,392
> > rate=59638.7 KB/s
> > 06-Jan 13:50 btape JobId 0: End of Volume "TestVolume1" at 397:1147 on
> > device "Superloader-Drive" (/dev/nst0). Write of 524288 bytes got -1.
> > 06-Jan 13:50 btape JobId 0: Re-read of last block succeeded. btape:
> > btape.c:2345 Last block at: 397:1146 this_dev_block_num=1147
> > btape: btape.c:2379 End of tape 397:0. VolumeCapacity=391,370,506,240.
> > Write rate = 59587.5 KB/s
> > Done writing 0 records ...
> > Wrote state file last_block_num1=1146 last_block_num2=0
> >
> >
> > 13:50:27 Done filling tape at 397:0. Now beginning re-read of tape ...
> > 06-Jan 13:50 btape JobId 0: 3301 Issuing autochanger "loaded? drive 0"
> > command.
> > 06-Jan 13:50 btape JobId 0: 3302 Autochanger "loaded? drive 0", result is
> > Slot 1.
> > 06-Jan 13:50 btape JobId 0: 3301 Issuing autochanger "loaded? drive 0"
> > command.
> > 06-Jan 13:50 btape JobId 0: 3302 Autochanger "loaded? drive 0", result is
> > Slot 1.
> > 06-Jan 13:50 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 1:626
> > Reposition from 1:626 to 397:1146
> > Reading block 1146.
> >
> > The last block on the tape matches. Test succeeded.
>
> So this looks very promising: 390 GB and I'm also seeing almost 60MB/s.
> I will repeat this test using one of the older tapes, then report back.
>
> Is it possible that the low block size of 64k affects tape capacity? It
> looks suspicious to me that all tapes "end" at about the same size...
It feels like the tapes really are worn out. I aborted the new btape
test since the throughput was really low:
14:31:54 Begin writing Bacula records to tape ...
Wrote blk_block=5000, dev_blk_num=1185 VolBytes=2,620,915,712 rate=24494.5 KB/s
Wrote blk_block=10000, dev_blk_num=464 VolBytes=5,242,355,712 rate=24845.3 KB/s
Wrote blk_block=15000, dev_blk_num=1650 VolBytes=7,863,795,712 rate=26656.9 KB/s
Wrote blk_block=20000, dev_blk_num=929 VolBytes=10,485,235,712 rate=24613.2 KB/s
Wrote blk_block=25000, dev_blk_num=208 VolBytes=13,106,675,712 rate=24590.4 KB/s
Wrote blk_block=30000, dev_blk_num=1394 VolBytes=15,728,115,712 rate=25532.7
KB/s
14:43:17 Flush block, write EOF
All the same config, just an older tape. :-( I'm not sure, how often
it's been used because of our rather complicted multi-stage backup
scheme (daily/weekly/monthly/yearly pools). Is it possible that the
drive simply wastes capacity because of low throughput?
What's your experience: How often may a tape be written to?
Thanks,
Tino.
--
"What we nourish flourishes." - "Was wir nähren erblüht."
www.lichtkreis-chemnitz.de
www.tisc.de
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