[Gllug] SCSI devices

[David Damerell]

On Thursday, 30 Aug 2001, Xander D Harkness wrote:
>I have a Surestore DLT Autoloader 818 (as previously mentioned ;-) 
>connected to a box running RH7.1 kernel 2.4.7-2
>I have devices under /dev/sg0, /dev/sg1, /dev/st0, /dev/sga, /dev/sgb, 
>/dev/nst0
>The device has 8 slots and the documentation for amanda implies that I 
>should be able to address the slots by /dev/nst0-7 (I cannot)

Obvious stupid stuff; does /dev/nst0 work for the first slot?

[The difference between /dev/nst0 and /dev/st0 is that the latter will
rewind automagically after each operation, and hence is usually
useless.] 

Do /dev/nst1-7 actually exist with the correct minor and major
numbers? A brief test suggests that, at least under Debian, they may
not;
damerell$ ls -l /dev/nst?
crw-rw----    1 root     tape       9, 128 Mar 30  1995 /dev/nst0
crw-rw----    1 root     disk       9, 129 Mar 30  1995 /dev/nst1

If not, use MAKEDEV to create them.

It would be interesting to know what is detected at boot time by the
BIOS and the kernel. Some such devices use a different LUN for each
tape slot; kernel and/or BIOS options to probe all LUNs for each SCSI
ID want to be on. (TBH, I've only seen this on CD multichangers; the
effect is that it appears to be six separate SCSI CD driver; but
apparently it does happen in tape drives as well.)

Some autochangers simply load the next tape whenever there is a
software request for tape ejection. Does an 'mt -f /dev/nst0 eject' do
anything useful?

-- 
David Damerell <damerell at chiark.greenend.org.uk> flcl?

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