[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [Bacula-devel] Rif: [Bacula-users] Virtual backup


On Wednesday 03 September 2008 14:50:56 Ferdinando Pasqualetti wrote:
> Hello Kern,
> thanks one more time for your work.
> I am trying to contribute to this discussion, even if I am sure that my
> knowledge is too weak.
> In my opinion you should allow to set a Next Pool also in a Virtual Backup
> pool (maybe also for Migration or Copy pool). This could be managed in a
> number of ways, i.e. you could set the Next Pool of the third pool to the
> second one, thus alternating the destination pools of the virtual backup.
> After the backup virtualization the source pools could be purged to make
> room for the next run.

There might indeed be some way to make this work, but I cannot clearly see how 
it would work automatically for multiple virtual backups.  

It would be very useful if you could show an explicit example with volumes 
(with specific names) in specific pools and how multiple virtual backups 
could work without eventually getting into a deadlock where Bacula wants to 
read and write the same volume or on the same device.

Regards,

Kern

> Best regards,
> --------------------------------------------------------------------------
> Ferdinando Pasqualetti
> G.T.Dati srl
> Tel. 0557310862 - 3356172731 - Fax 055720143
>
> bacula-users-bounces@xxxxxxxxxxxxxxxxxxxxx wrote on 03/09/2008 11.37.57:
> > Hello,
> >
> > As many of you know Virtual Backup (consolidation, synthetic full, ...)
>
> is a
>
> > new feature that is implemented in the development trunk and scheduled
>
> to be
>
> > released later this year.  It essentially copies what would be a "full
> > current" restore to a new Volume thus creating an virtual backup that
>
> can
>
> > serve as a Full backup.  This has a lot of advantages, particularly for
>
> sites
>
> > with full backups that run long times or for remote sites where the time
>
> to
>
> > transmit a full backup is excessive.
> >
> > The Virtual Backup feature works much like Migration and Copy.  It reads
>
> from
>
> > the required Volumes and writes to a Volume specified in the pool as
>
> "Next
>
> > Pool".  This ensures that the read and write Volumes are different.
> >
> > Everything seems to work fine with the Virtual Backup.  However,
>
> thinking
>
> > about longer term operations, it has occurred to me that when you want
>
> to
>
> > make a second Virtual Backup things will become very complicated. First,
>
> the
>
> > Virtual backup will want to read the previous Virtual backup volume,and
>
> then
>
> > if that Volume is not full, it will want to write to the same Volume.
>
> Even
>
> > if the volume is full, you will be in a situation where the Job will
>
> want to
>
> > read and write to volumes in the same pool.  In all those cases, there
>
> is no
>
> > guarantee that there will not be a deadlock situation (actually Bacula
> > currently cancels any job attempting to read and write from the same
>
> Storage
>
> > device).
> >
> > I am not 100% sure what to do to resolve this issue.  I suppose one
>
> could run
>
> > a Migration job to "move" the Virtual Backup back to the Pool from which
>
> it
>
> > originally came, then the next Virtual Backup would work fine (the same
>
> as
>
> > the first one), but that sounds a bit kludgie.
> >
> > If anyone has any suggestions, I would appreciate to hear them. However,
> >
> > suggestions that require implementing significant amounts of code or
>
> complex
>
> > new algorithms such as deadlock detection won't be very helpful since
>
> there
>
> > is no time left to do such implementations between now and release time.
>
>  In
>
> > addition, deadlock detection won't help, what we really need is deadlock
> >
> > resolution, and that is an even more difficult subject.
> >
> > Best regards,
> >
> > Kern
>
> -------------------------------------------------------------------------
>
> > This SF.Net email is sponsored by the Moblin Your Move Developer's
>
> challenge
>
> > Build the coolest Linux based applications with Moblin SDK & win great
>
> prizes
>
> > Grand prize is a trip for two to an Open Source event anywhere in the
>
> world
>
> > http://moblin-contest.org/redirect.php?banner_id=100&url=/
> > _______________________________________________
> > Bacula-users mailing list
> > Bacula-users@xxxxxxxxxxxxxxxxxxxxx
> > https://lists.sourceforge.net/lists/listinfo/bacula-users



-------------------------------------------------------------------------
This SF.Net email is sponsored by the Moblin Your Move Developer's challenge
Build the coolest Linux based applications with Moblin SDK & win great prizes
Grand prize is a trip for two to an Open Source event anywhere in the world
http://moblin-contest.org/redirect.php?banner_id=100&url=/
_______________________________________________
Bacula-devel mailing list
Bacula-devel@xxxxxxxxxxxxxxxxxxxxx
https://lists.sourceforge.net/lists/listinfo/bacula-devel


This mailing list archive is a service of Copilot Consulting.