Bug#675934: st - slow tape read/write rate

[Jonathan Nieder <jrnieder@gmail.com>]

Hi Yury,

Yury O. Tabolin wrote:

> I have slow tape read/write rate after upgrade from Lenny with the
> old kernel 2.6.18 to Squeeze. Everything worked well except the tape
> library HP StorageWorks MSL 4048 Ultrium 960, connected to it via
> SCSI Megaraid 320-2x. It has become very slow.

Thanks for reporting it.  Let's see:

[...]
> st: Version 20081215, fixed bufsize 32768, s/g segs 256
> st 2:1:4:0: Attached scsi tape st0
> st 2:1:4:0: st0: try direct i/o: yes (alignment 4 B)
> scsi_id[5933]: segfault at 0 ip (null) sp 00000000ffcd29a0 error 14
> scsi_id[5930]: segfault at 0 ip (null) sp 00000000ffc0cf60 error 14
> st0: Block limits 1 - 16777215 bytes.
[...]

Worrisome.  Can you get a backtrace from this segfault?  udev
maintainers, any advice on how to do so?

Aside from that:

Please attach full "dmesg" output from trying 2.6.32-45 from squeeze
and a 3.x.y kernel from sid, experimental, or squeeze-backports.  The
only packages that should be needed from outside squeeze for this test
are the kernel image itself, linux-base, and initramfs-tools.

If the bug is still reproducible with a 3.x kernel, we can get help
from upstream.  If not, we can try to find what change fixed it and
apply the same fix to squeeze.

Hope that helps,
Jonathan