PV-124T shoe shining on PE2950

[Jesús M. Navarro]

Hi all:
I've got a new PE2950 2GB RAM with an Adaptec 39230A which links to a PV124T 
LTO2.  That's the only device on that SCSI chain, since disks (2xRAID1 + 
4xRAID5) are attached to a PERC5/i.  The operative system is Debian "Etch" 
amd64 (that's the arch for all x86_64 CPUs).

The problem is that I can't make the tape stream, it just shoe shines at about 
2MB/s.

For instance:

time -p dd if=/dev/zero of=/dev/tapenorewind bs=64k count=16384

This should move data to the tape as fast as possible but the drive seems to 
stream for some three/four seconds then stops for about ten seconds and then 
starts again, so the overall result is being terribly slow (as I said, it 
averages at about 2MB/s).

I tested this both moving zeroes as in the previous example as well as moving 
a 2GB file (a dump image) or data directly from a partition, either with dd, 
dump or tar with exactly same results, so I think it must be some issue 
either with the tape drive itself or some config parameter regarding the 
Adaptec.  Moving data from disk to disk (ie. from the RAID5 array to the 
RAID1) averages a bit over 30MB/s which seems reasonable (while not 
brilliant).  I already upgraded the firmware both for the drive and the tape 
changer just in case.

Any help or ideas?
-- 
Jesús M. Navarro
Jefe de Sistemas y Soporte
Ándago Ingeniería - www.andago.com