Very slow certance lto-2 ultrium

[John Schleigh]

I have seen some mention of this, but no solutions yet.

Can someone help me to understand what I need to do to get better than 2.7Mb/s 
transfer rate on this Certance Ultrium 2 tape drive?  It should be able to 
get closer to 20Mb/s.

I have been guessing that I need to set the right blocking factor or 
something, but I really don't know.  I have tried piping tar to mbuffer, 
large block sizes, small block sizes.  Regardless, my shoes are very shiny.

# mt -f /dev/nst0 status
drive type = Generic SCSI-2 tape
drive status = 1107296256
sense key error = 0
residue count = 0
file number = 0
block number = 0
Tape block size 0 bytes. Density code 0x42 (unknown).
Soft error count since last status=0
General status bits on (41010000):
 BOT ONLINE IM_REP_EN

Linux pe2900 2.6.16.46-0.12-smp #1 SMP Thu May 17 14:00:09 UTC 2007 x86_64
SLES 10