[Techtalk] SCSI tape drive not recognized

[John Clarke]

On Tue, Jan 18, 2005 at 03:32:49 -0800, Lucky Lady wrote:

> I'm migrating our backup duties to another server. My
> SCSI card and SCSI tape drive *appear* to be
> recognized (i.e. they are visible in the "Hardware
> browser" window). However when the computer boots, I
> do not see the tape drive.  

I don't know what you've tried, or how much you know about kernel
modules, so I'll suggest a few things to try.

First, check whether the necessary modules are loaded, e.g.:

    [root at dropbear ~]# lsmod |egrep '^(sd|st|sg|aic|scsi)'
    st                     29520   0 (autoclean)
    aic7xxx               132224   0 (autoclean)
    scsi_mod              105132   3 (autoclean) [st aic7xxx]

If not, try to use the drive and see if they're automatically loaded. 
I'd use "mt" for this, but if you don't have it, you can write a small
amount of data with tar instead.  e.g.:

    [root at dropbear ~]# mt -f /dev/st0 status
    SCSI 2 tape drive:
    File number=-1, block number=-1, partition=0.
    Tape block size 0 bytes. Density code 0x0 (default).
    Soft error count since last status=0
    General status bits on (50000):
     DR_OPEN IM_REP_EN

Or to use tar:

    [root at dropbear ~]# dd if=/dev/zero of=temp bs=512 count=1
    1+0 records in
    1+0 records out
    [root at dropbear ~]# tar -f /dev/st0 temp
    (I'm not showing the output from this command because I don't have a
    tape in the drive and it's 20km away so I can't put one in ;-)

Then you should be able to run lsmod again and see the modules (they'll
stay loaded for a few minutes).

If you can't see the modules, then it's either because autoloading is
disabled (unlikely if you're using RH's kernel), or because
/etc/modules.conf isn't setup properly.  Try loading them manually:

    [root at dropbear ~]# modprobe st

If this doesn't work, then it could be that you don't have an alias for
scsi_hostadapter in /etc/modules.conf.  Try:

    [root at dropbear ~]# modprobe aic7xxx
    [root at dropbear ~]# modprobe st

If this now works, then you simply need to add this:

    alias scsi_hostadapter aic7xxx

to /etc/modules.conf andr un "depmod -a" to recalculate the module
dependencies.  Then remove the modules with "modprobe -r st" and 
"modprobe -r aic7xxx".  Now try running mt or tar again.  It should work
this time.  Let me know if it doesn't and I'll see what else I can do to
help.

This won't fix you problems, but I suggest you upgrade your kernel and
other packages.  RH 9 is old and no longer supported by RH, but Fedora
Legacy (http://fedoralegacy.org/) has released a lot of updates.  The
latest kernel is kernel-2.4.20-37.9.legacy.

> I have no idea where the documentation is for either
> the SCSI card or the SCSI tape drive.

I've used four different scsi tape drives and three different SCSI cards
and not had documentation for any of them :-)


Cheers,

John
-- 
Except in teco the line noise would be syntactically valid.
            -- Peter da Silva