Ray,
The problem has to do with the speed negotiation that occurs on
driver initialization.
That I know of, there are 2 ways to address the problem.
For kernel 2.6.17 (and later), you can go into the Adaptec scsi bios
and explicitly limit the transfer speed for the target device to 160
MB/s.
Alternatively, for kernel 2.6.16 (and later), you can add the
following to your boot init file:
# Fix scsi speed negotiation on tape drive
SYS_TAPE=/sys/class/spi_transport/target0:0:3
echo "12.5" > $SYS_TAPE/min_period
echo "1" > $SYS_TAPE/revalidate
[Remember to change the SYS_TAPE variable to match your target device]
You will know that you've done it correctly when you see 160MB/s as
the value of User/Goal/Curr for your target in /proc/scsi/aic79xx/*.
In my case, it's still unclear to me whether or not the problem is
the AIC79xx, the HP LTO drive, or the scsi driver.
Hope this helps.
Denny
On Nov 23, 2006, at 11:40 , Raymond Scholz wrote:
Hello Denny,
sorry for bothering you with this but I spent the whole day searching
the net for the reason why our SCSI LTO-2 tape suddenly dropped
performance down to 2MB/s after upgrading the Linux kernel.
Your description and hardware comes close to the behaviour we
observed:
http://www.spinics.net/lists/linux-scsi/msg06003.html
http://thread.gmane.org/gmane.linux.scsi/22010/focus=22021
Did you receive any response or (even better) found a better solution
than downgrading the kernel?
Cheers, Ray
--
Raymond Scholz - rscholz@xxxxxxxx - GnuPG/PGP - http://www.zonix.de/
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