On Tue, Jul 11, 2006 at 09:07:32PM +0930, Jerlique Bahn wrote:
> 
> > Yes, it will do a read of the entire tape.  There is a config file option
> > called amrecover_do_fsf that if set to true will fsf your tape to the
> > correct spot if your drive supports it, which is much faster than a linear
> > read.
> 
> I do have that set, and the drive finished up in about 1 hour.  It obviously
> worked, because the full dump takes about 20 hours.
> 
...

> SRV# ammt -f /dev/nsa0 rewind
> SRV# dd if=/dev/zero of=/dev/nsa0 bs=32k count=10000
> 10000+0 records in
> 10000+0 records out
> 327680000 bytes transferred in 122.037586 secs (2685074 bytes/sec)

Jerlique,

I'd say stop looking at amanda as the source of slow dumps.
Your dd command uses a data source (/dev/zero) that can provide
data faster than any disk file or network and it is being fed
directly to the tape drive through one of the more efficient
system, not amanda, commands (dd).  Anything else introduced
to the mix could only slow things down.

Yet, despite the use of these efficient/fast components you
are still seeing a tape write speed of only 2.685 MB/sec.
LTO-2's are rated at over 10 times that speed.  Corresponding
to your 20 hour dumps is the math that say it takes over 20 hr
to record 200 GB at 2.685 MB/sec.

Look to your system, card slot to controller to cables to drive
to terminator for the reason for low write performance.  Only
after you get a dd command like you show above to perform close
to the drive's capability will tuning amanda be reasonable.


-- 
Jon H. LaBadie                  jon AT jgcomp DOT com
 JG Computing
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