In the message dated: Fri, 01 Dec 2006 17:31:55 GMT,
The pithy ruminations from Alan Brown on
<Re: [Bacula-users] Fatal error - attempt to load empty slot in autochanger> we
re:
=> On Fri, 1 Dec 2006, Kern Sibbald wrote:
=>
=> > It appears to me that you have run into some sort of race condition where
two
=> > threads want to use the same Volume and they were both given access.
I run into this condition* about 2~3 times per month.
* Possibly from a different cause, but the results are the same.
I'm running 1.38.11 under Linux, with a 23-slot, 2 drive autochanger.
=> > Normally that is no problem. However, one thread wanted the particular
=> > Volume in drive 0, but it was loaded into drive 1 so it decided to unload
it
=> > from drive 1 and then loaded it into drive 0, while the second thread went
on
=> > thinking that the Volume could be used in drive 1 not realizing that in
=> > between time, it was loaded in drive 0.
=>
=> Someting similar has happened here today, except that one job is now
=> hanging waiting for the tape that's in the other drive.
Yes, that's pretty frequent here too.
=>
=> > I'll look at the code to see if there is some way we can avoid this kind of
=> > problem. Probably the best solution is to make the first thread simply
start
=> > using the Volume in drive 1 rather than transferring it to drive 0.
That would be terrific.
In the next few weeks I will have access to a second auto-changer with a
similar configuration. Before that unit is put into production use, I can set
up test installs of Bacula if you would like me to run field tests to debug the
autochanger code.
=>
=> This would be good.
=>
=> Removing an apparent bias towards using Drive0 would be good too, as it
=> causes uneven wear on the drives.
Good point.
=>
=> AB
=>
----
Mark Bergman [EMAIL PROTECTED]
System Administrator
Section of Biomedical Image Analysis 215-662-7310
Department of Radiology, University of Pennsylvania
http://pgpkeys.pca.dfn.de:11371/pks/lookup?search=mark.bergman%40.uphs.upenn.edu
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