Networker

Re: [Networker] Detecting cleaning required

2004-01-05 11:16:18
Subject: Re: [Networker] Detecting cleaning required
From: Tim Mooney <mooney AT DOGBERT.CC.NDSU.NODAK DOT EDU>
To: NETWORKER AT LISTMAIL.TEMPLE DOT EDU
Date: Mon, 5 Jan 2004 10:16:09 -0600
In regard to: Re: [Networker] Detecting cleaning required, Davina Treiber...:

>I couldn't see anything else that looked promising, so
>still open to suggestions. Surely there must be something in the public
>domain that might do this.

Your question last week really got me going on this again too.  I think
I had better luck than you did.

Our networker server is a Red Hat Linux box, so I started looking at
what's available for Linux.  I want something that's cross (UNIX) platform
too, but I can likely write what I need if I can see a good enough example
for at least one platform.  My problem is that although I've been using
SCSI devices for years, I still only have a vague notion of how SCSI
commands work and what you can expect in each "phase" of the protocol.
I think once I get an understanding of this fundamental bit, the rest will
be straight-forward.  ;-)

In any case, I started looking at tools for Linux, to see what kinds of
examples are out there.  In addition to the Legato-provided binaries,
we use `mtx' to do certain jukebox tasks, such as peek at what's in the
14 load ports of our 9710.  I also know about the Linux "SCSI Generic"
(sg) device, but I didn't know a lot about what kinds of tools were
available with it.  The source distribution for

        sg3_utils-1.06.tgz

has a large number of utility programs for sending various SCSI commands
through the Linux SCSI generic device.  One of these (sg3_logs) is capable
of sending a LOG SENSE command.  Using it with our tape drives, I'm able
to get back the hex response, but I'm still not 100% certain how to decode
the entire block I get back.  For example, if I run

        sg_logs -p=3e -paramp=1 -h /dev/sg6

on our Linux NetWorker server with a SuperDLT1 on /dev/sg6, I get back:

Returned log page code=0x3e,  page len=0x28
 00     3e 00 00 28 00 01 60 04  00 00 00 00 00 02 60 04
 10     00 00 08 f2 00 03 60 04  00 00 00 05 00 04 60 04
 20     01 05 03 0e 00 05 60 04  00 00 00 1a


Based on how I read the "Quantum DLT7000 Tape Drive" manual (section
5.4.8.6) and the "SDLT 220 and SDLT 320 SCSI Interface Guide" (which I
found at:

        
www.quantum.com/NR/rdonlyres/A2A6B063-BF48-4665-B38C-322DE316E88E/SCSIInterfaceGuide/SCSIMessages.pdf

I'm looking at section 4.8.9 in that guide), I don't see why I'm getting
back 28 bytes.  It looks to me like the response should be much shorter,
which just reinforces that I'm missing some critical bit of knowledge.
Because the length of the returned data is so much larger than I was
expecting, I'm not certain where the bytes (or byte) I'm interested in is.

>I would use jukebox
>firmware controlled cleaning, but the problem is the visibility of when
>the cleaning tapes need replacing.

That's exactly why this problem is interesting to me too.  Our jukebox is
located in a different building way across campus.  It's a fine field trip
spring through fall when the weather is nice, but on a day like today,
when it's -15 F outside, I would rather check the cleaning status from the
comfort of my office.

I'm going to continue looking at this problem in my spare time, now that
I know for certain that there *is* a way to do what I want.  I'll report
back when I have any interesting status information.  I expect it will
be at least a couple weeks.

Tim
--
Tim Mooney                              mooney AT dogbert.cc.ndsu.NoDak DOT edu
Information Technology Services         (701) 231-1076 (Voice)
Room 242-J6, IACC Building              (701) 231-8541 (Fax)
North Dakota State University, Fargo, ND 58105-5164

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