[Bacula-devel] RFC: "Recycle Current Volume"

[Nic B. <lis...@be...>]

Hi,
	I'm using Bacula 1.30a at a few client sites, backing up somewhere
around 500GB at the moment. One problem I've run into is with clients
that want rotation schedules that have tapes labeled for each day of the
week, "Monday", "Tuesday", etc.

This works fine, including volume recycling, if the tape is put in every
day without fail. As soon as a day is forgotten, without intervention by
myself, things quickly turn to custard.

Eg. Monday-Thursday, differential backups against a full backup done
each Friday. After a week where all backups ran happily, and the volumes
were marked used via Max Volume Jobs or Volume Use Duration, things look
like this:

Tape      | Status
----------+--------
Monday    | Used
Tuesday   | Used
Wednesday | Used
Thursday  | Used

Now, on Monday, the Monday volume is recycled, but nobody put the tape
in, and we end up with:

Tape      | Status
----------+--------
Monday    | Recycle
Tuesday   | Used
Wednesday | Used
Thursday  | Used

When we get to Tuesday, the "Tuesday" tape is inserted. This is where
things fall down - the director will complain "1998 Volume blah not
Append or Recycle", and request the recycled "Monday" tape. To get the
tapes back in sync with the real day of the week, I have to fiddle
around updating the volumes manually.

What I've done is whip up a patch that basically implements "Recycle
Current Volume" - when the jobs run on a Tuesday, they'll see that
time(now) > current_volume->lastwritten + current_volume->volretention,
and will attempt a prune. If the prune results in all records being
removed, it will then recycle it for immediate use.

This is not perfect: Monday will be marked recycled, although there's
actually still going to be valid data on the tape.

Where the "request for comments" portion of this email comes in is here:
	
	Is this feature going to be useful enough to include in the
	mainline distribution, ie. should I develop it fully, adding
	it as a pool configuration option etc., or should I not bother
	developing it beyond an always-on kludge for my own use?

Patch is attached; testing so far is not much beyond "it compiles", so
any comments would be appreciated.

Regards,
	Nic.

-- 
Nic Bellamy <ni...@be...>
Bellamy Consulting (NZ) Limited. +64-6-377-4957 Mobile: +64-21-251-8954
Internet Software & Security Consulting -- http://www.bellamy.co.nz/ --