RE: [Bacula-users] Problem with mtx-changer when library loses which slot for a tape

[Tom B. <tb...@da...>]

I believe the problem is with the mtx-changer loaded command. Here is
the errors from the messages for one of the jobs that failed:

01-Oct 03:05 solweb-dir: Start Backup JobId 451,
Job=3Dsolweb-0.2005-10-01_03.05.00 01-Oct 03:06 solweb-sd: 3301 Issuing
autochanger "loaded drive 0" command.
01-Oct 03:06 solweb-sd: 3302 Autochanger "loaded drive 0", result:
nothing loaded.
01-Oct 03:06 solweb-sd: 3304 Issuing autochanger "load slot 2, drive 0"
command.
01-Oct 03:06 solweb-sd: solweb-0.2005-10-01_03.05.00 Fatal error: 3992
Bad autochanger "load slot 2, drive 0": ERR=3DChild exited with code 1.
01-Oct 03:06 solweb-fd: solweb-0.2005-10-01_03.05.00 Fatal error:
job.c:1597 Bad response to Append Data command. Wanted 3000 OK data ,
got 3903 Error append data

When I looked - the drive was full, but the autoloader did not know
where the tape should go. I believe when I ran an mtx status Data
Transfer Element 0 had the following:

Data Transfer Element 0:Full (Unknown Storage Element Loaded)

And the mtx-changer loaded 0 command returned "Element" which bacula
interpreted as "nothing loaded"

Mtx-changer needs to be made smarter to take into account that the tape
library may lose track of tapes so it will need to feed back something
to indicate that it doesn't know where the tape needs to go. Here are
the steps I believe need to be addressed:

1) mtx-changer loaded $drive returns a slot number, empty indicator or
unknown slot

2) a slot number or empty are taken care of already... proceed.

3) What do we do with an unknown tape?
	Check bacula to see which slot the tape needs to go into
	Check to see if the slot is empty
		If it is empty then unload the tape to that slot
		If it is Full then search for the next "Empty" slot
		Unload tape to the empty slot
		If the slot unloaded to =3D slot from bacula then we are
okay
			Otherwise we need to update the DB to now
reflect the true
			Location of the tape.

How do you get bacula to pass the slot it thinks the tape should go into
to mtx-changer?

Very rough but it is a start...

Tom.
----
Thomas Boyda
tb...@da...
276-739-2314=20
-----Original Message-----
From: Alan Brown [mailto:aj...@ms...]=20
Sent: Tuesday, October 04, 2005 6:00 AM
To: Arno Lehmann
Cc: Kern Sibbald; bac...@li...; Tom Boyda
Subject: Re: [Bacula-users] Problem with mtx-changer when library loses
which slot for a tape

On Tue, 4 Oct 2005, Arno Lehmann wrote:

> Most certainly. The problem in this case might be to reproduce the
situation=20
> - as far as I understood Tom, he didn't change the tape inventory, but
the=20
> autochanger somehow lost track of the slots used. I heard that before,
and,=20
> although seldom, some autochangers seem to forget their inventory from
time=20
> to time.

This definitely happens if the power is cycled. Very few loaders keep=20
stateful information about what drive-mounted tape came from which slot
in=20
such a case.

> Manually moving tapes is a good way for testing the robustness of=20
> bacula / mtx-changer, though :-)

Most loaders will rescan their contents after any manual intervention,
so=20
their results will always be up to date unless there's been a power=20
failure.

Having said that I've fooled our HP/Overland changer by opening the lid=20
and switching tapes around, but that was desparation measures to try and

unload a wedged tape and required a screwdriver - hardly day-to-day=20
activity (periodic MTX "inventory" commands would spot this of course)

AB