Simon wrote:
On Dec 21, 2005, at 4:33 AM, Nigel Wade wrote:
You ought to have a different sg device for each LUN if sg is working
correctly. At least that's what I get for multiple LUNs on a SCSI
RAID. Each LUN on the RAID has a different sg device, and is mapped
to a different sd device.
What is the contents of /proc/scsi/sg/devices? This should show you
the SCSI id and LUNs of all identified SCSI devices on the system.
Well, it doesn't mean much to me, but here it is:
[root@www4 ~]$ cat /proc/scsi/sg/devices
1 0 0 0 0 1 4 0 1
1 0 1 0 0 1 4 0 1
1 0 8 0 3 1 2 0 1
2 0 0 0 0 1 63 0 1
2 0 15 0 3 1 3 0 1
2 1 5 0 1 1 3 0 1
2 2 15 0 3 1 3 0 1
It's only telling you the same info as sg_scan does, but in a much less
understandable format. Column 1 is the controller number, column 2 is the
channel, column 3 is the SCSI id and 4 is the LUN. The others are to do with
device types.
Do you have sg3_utils installed? If not I'd suggest doing so, this
package really helps with sorting out sg/st/sd assignments. For
example, sg_scan on my system show this:
Yep:
[root@www4 ~]$ sg_scan -i
/dev/sg0: scsi1 channel=0 id=0 lun=0
IBM-ESXS MAP3735NC FN C101 [rmb=0 cmdq=1 pqual=0 pdev=0x0]
/dev/sg1: scsi1 channel=0 id=1 lun=0
IBM-ESXS VPR073C3-ETS10FN S370 [rmb=0 cmdq=1 pqual=0 pdev=0x0]
/dev/sg2: scsi1 channel=0 id=8 lun=0
IBM 39M6750a S320 0 1 [rmb=0 cmdq=0 pqual=0 pdev=0x3]
/dev/sg3: scsi2 channel=0 id=0 lun=0
IBM SERVERAID 1.00 [rmb=0 cmdq=1 pqual=0 pdev=0x0]
/dev/sg4: scsi2 channel=0 id=15 lun=0
IBM SERVERAID 1.00 [rmb=0 cmdq=0 pqual=0 pdev=0x3]
/dev/sg5: scsi2 channel=1 id=5 lun=0
HP Ultrium 3-SCSI G37B [rmb=1 cmdq=0 pqual=0 pdev=0x1]
/dev/sg6: scsi2 channel=2 id=15 lun=0
IBM EXP400 S320 D110 [rmb=0 cmdq=0 pqual=0 pdev=0x3]
(that's a useful tool - cheers :-)
Ok, so the only device on scsi2, channel 1 is the Ultrium tape drive. No sign of
your tape changer. It looks like the system isn't set up to scan LUNs. I don't
know of any way to fix that on a live system without shutting down all SCSI
devices and unloading the SCSI drivers.
Incidently, I have this entry in /etc/modprobe.conf:
options scsi_mod max_luns=32
... and I think that's the difference - this was what Matt Brookover
suggested as well :-)
I'm waiting for a new machine to arrive before I go fiddling with
devices though, in case anything bad happens. The entire machine is
SCSI, internal and external RAIDs, and I don't want there to be any
surprises on a currently-active machine :-)
It's almost guaranteed that if something can go wrong, it will go wrong, and at
a time which will cause the most embarassment and damage.
--
Nigel Wade, System Administrator, Space Plasma Physics Group,
University of Leicester, Leicester, LE1 7RH, UK
E-mail : nmw@xxxxxxxxxxxx
Phone : +44 (0)116 2523548, Fax : +44 (0)116 2523555
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