Controling transfer rate of SCSI for Peregrine Tape drive...

[Robert G. Brown]

On Wed, 24 Jun 1998, Peter VanVleet wrote:

> 
> 	I have an Adaptec 7880 chipset, and a Seagate Peregrine Tape drive.
>  I'm running Red Hat Linux 5.0, with kernel 2.0.32. When writing larger files 
>  to the tape (i.e. backups) the system often hangs. It seems especially
>  sensitive to other activity on the system. 

Check your termination.  I've gotten multiple systems from vendors
with termination anything from nonexistent to redundant (both
technically broken).  The problem is nearly universal on internal
drives on internal cables from some vendors.  This will usually leave
the system nominally functional (it will boot) but screws things up
when a high traffic burst comes along.  Some SCSI devices appear to be
worse than others about termination issues, and on my systems bad
termination has proven quite capable of causing an "inexplicable"
crash (no visible cause in the logs, just instant death).  Presumably,
if (for example) a drive screwed up during a paging process for a
kernel function it could instantly trash the core kernel...

IMHO, the "best" thing to do about internal termination is to buy
preterminated cables or external terminators and not to try to
terminate drives via jumpers or those little bitty terminating
resistors at all.  There is a really good termination URL I found once
(that describes, e.g.  "active" vs "passive" termination) but
unfortunately I can't remember where...

   rgb

Robert G. Brown	                       http://www.phy.duke.edu/~rgb/
Duke University Dept. of Physics, Box 90305
Durham, N.C. 27708-0305
Phone: 1-919-660-2567  Fax: 919-660-2525     email:rgb at phy.duke.edu




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