topic Re: scsi device problem in Operating System - Linux

scsi device problem

Jun Zhang_4 — Sat, 24 Apr 2004 14:51:20 GMT

I have a Exabyte tape drive on Adaptec 2940. Once the RH9 boot up, and I do
cat /proc/scsi/scsi
I get
Attached devices: none
Then I do
mt -f /dev/st0 status
the tape drive is recognized (cat /proc/scsi/scsi get the right output).
What is the problem?

Jun

Re: scsi device problem

Steven E. Protter — Sat, 24 Apr 2004 22:27:36 GMT

Most of the time when this happens to me, and it does, its fixed by replacing the scsi cable. Even if there is no obvious damage.

The good news is most cables cost under $50, though don't bother with most local computer stores, you have to order it.

Check the cables, check device power and try a different cable. That solves the problem 75% of the time with me, any OS.

SEP

Re: scsi device problem

Martin P.J. Zinser — Sun, 25 Apr 2004 10:31:04 GMT

Hello,

if what Jun reports is acurate (i.e. device becomes reliably avaialbe after the first mt status), it does not look like a HW problem to me. I am not overly familiar with the module loading process, but it would seem that the module is only loaded in that case if the device is actually used, kind of a deferred loading.

Jun, could you do a lsmod before and after the mt status the next time you reboot to see if the driver has been loaded?

Greetings, Martin

Re: scsi device problem

Roberto Polli — Mon, 26 Apr 2004 06:14:38 GMT

I'm with Martin.Linux should load the scsi module (sg or/and st) only when you try to access any particular device.

Take a look @ /etc/modules.conf
Peace, R>

Re: scsi device problem

Matt Palmer_2 — Wed, 05 May 2004 03:23:53 GMT

have you had a look inside /var/log/messages??

I have had this problem before, and noticed that messages is full of 'not enough mtrrs'. Not sure what they are but this only happens if I add a tapedrive after initial install of the OS, otherwise I do not have the problem accessing /dev/st0

Re: scsi device problem

Roberto Polli — Wed, 05 May 2004 03:44:16 GMT

Matt,
I remember that 'not enough mtrr' -memory type range register- is a CPU stuff, maybe it's an error given _while_ but independently from tape.
I know MTRR are couples (memory,bus) that fasten register's access with processors>P2
eg. a MTRR can address a particular device to use a specific range of memory. If it's not clear or wrong, please, let me know.

Peace, R.

Re: scsi device problem

Matt Palmer_2 — Wed, 05 May 2004 04:32:55 GMT

Hi Roberto,

I found the answer in an unrelated post.

Apparently MTRR problems can be related to memory leaks in low memory, and can sometimes sorted out by disabling shared memory in the BIOS for things like integrated graphics cards,etc. This is exactly the config on the server I have, i.e:it is using shm to support the onboard VGA. So I'm going to disable it and put a PCI VGA in instead, and see how I go with the drive.

thanks for the help, maybe this could be a way forward for the poster of this message to.

regards

Matt

Re: scsi device problem

Roberto Polli — Wed, 05 May 2004 10:06:47 GMT

Jun,
does any give answer help you?
did you solve it?

Peace, R.