Weird behaviour of AIT-3 and (g)tar

[Tulio Guimarães da Silva]

Hello again,

    I´m having some trouble putting a Sony SDX-700V SCSI AIT-3 unit to 
work on FreeBSD 5.3-RELEASE.
  The first issue is: it runs toooooooo slow. Transfers with tar 
(whithout -j, -z and such) or "cat file >/dev/sa0" go at about 800kB/s, 
though it should be more than 10MB/s. This wouldn´t be a big issue, but 
then comes the second problem...
  Besides the speed, hardware compression seems to not being funcional 
either. I already tried every 4 possible dip switch setting for 
compression, but I am still not able to transfer a 180GB archive to a 
(should-be) 260GB medium. And when I thought I could live with that...
  Third problem: tar does not (re)store all files, specially when I set 
block ("-b") sizes. With -b 64 and upper, tar would end perfectly and 
fast, but when trying to restore or list it ends prematurely; i´m now 
trying to test with -b 10, but it´s already taking more than 20 hours to 
complete the transfer, and I don´t know if it will end before this 
weekend. :)
  There´s no change if I use tar or gtar. :(
  Now for the environment:
HP ML 110 server, 2.8 GHz HT (enabled)
4x80GB SATA disks in RAID5 on a HighPoint Rocket Raid 1820A
Adaptec 2940UW or Ultra160, doesn´t matter...

  I think i´m using correct cabling :) ; with the 2940UW I use a 
standard flat-68 and termination on the device, or, the Ultra160 goes 
with a terminated 2-device twisted flat cable on the card´s LVD 
connector (not the SE). That´s what we use for other SCSI machines too.
  Is there any known issue with AIT-3 tapes? Am I missing or doing 
something wrong? Should I change to another backup software?
  Well, thanks again for your attention. Ideas are *very* welcome.

Tulio