FWD'd on behalf of a co-worker who is stuck in some limbo dimension caused by the SF.net mailman farm.
----
From: Steve Polyack <[EMAIL PROTECTED]>
To: [EMAIL PROTECTED]
Subject: FreeBSD, Bacula, and a Dell Autochanger
Date: Tue, 25 Nov 2008 15:23:39 -0500
We've been using Bacula with FreeBSD with a Dell Autochanger (PV-122T)
for some time now. Within the last few months we've seen the interface
to the tape changer crash, causing the devices /dev/ch0 and /dev/nsa0 to
disappear. Re-scanning the SCSI bus with camcontrol(8) brings the devices
back just fine.
Physical problems with the changer have been ruled out
by replacing it (twice!). We've also added a good bit of debugging to
chio-changer.sh (Bacula's freebsd interface to the changer) to get a
better look at the problem.
Anyways. we've witnessed the crash while the changer was unloading a
tape. After rescanning the bus and checking the device with chio(1) we
can see that the tape unload occurred successfully. This has led us to
believe that FreeBSD is not giving the device enough time to complete
its operations ((ch0:ahc0:0:5:0): SCB 0x2 - timed out), and is giving up
after timing out. For example:
static const u_int32_t CH_TIMEOUT_EXCHANGE_MEDIUM = 100000;
... does not seem to be adequate, as we've seen the device take upwards of
two minutes to exchange a tape! We've doubled most of the timeouts in
/usr/src/sys/cam/scsi/scsi_ch.c and the problem has yet to reoccur.
Has anyone else ever had an issue similar to this? Is there a better
solution, or a more likely problem that we are potentially missing?
Perhaps a sysctl knob would be appropriate instead of static inline values?
--
Brian A. Seklecki <[EMAIL PROTECTED]>
Collaborative Fusion, Inc.
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