On Tuesday 08 September 2009 13:16:37 Gavin McCullagh wrote: > Hi, > > On Sat, 05 Sep 2009, Kern Sibbald wrote: > > I don't think you have looked into the possibility of doing separate > > "long term" backups to tape. If you do it correctly, I am not convinced > > that the growth in data is as bad as you say. If you do a Full once a > > year then incrementals once a month, I think you will have a reasonable > > solution. > > A second independent backup cycle is an option I hadn't considered and it > would reduce the duplicated data a fair bit. It's obviously also possible > on either type of media (disks/tapes). It does involve running extra > backup jobs but we can probably survive that. > > I'll talk to the budget master about organising disk/tapes for the > long-term archival, thanks. > > > I have never understood your "system". From what I see you are proposing > > to make incrementals back in time -- that is something that I do not > > think is possible and with the information you supplied, I could not > > imagine any practical way to implement a working solution. It could be > > that I am missing something. > > As I've not explained well enough yet, you might humour me to try > explain once more. It's starting to sound like this may be impossible, but > I'm unclear why so I'd at least like to understand that. I apologise if > this seems like a waste of your time. > > My notion of incremental datasets is that they're somewhat like a > multi-file patch which tells you how to turn dataset1 into dataset2 by > describing the files which have changed. In general dataset2 is dataset1 > at some later date. I'm breaking that assumption, so perhaps that's where > things go wrong. As incremental backups bring you forward in time, suppose > we call this decremental backups. > > If you have full monthly backup datasets from January to September, is it > (theoretically) possible to create a decremental dataset which, applied to > February could give you the dataset from January? If you could do that, > you could delete the full backup from January and free up space from the > data which was in both sets. You could then do the same with > February/March, etc. and still get back to January using the two > decremental datasets and the full job from March.
I think I now understand what you are asking for. You want to have Incremental Jobs go forward in time from a Full (current behavior) and incremental (decremental) jobs that go backward in time. Those reverse incremental jobs would be something synthesized from the Full in question and a previous Full. The reason is that this would allow one Full to cover twice the period of time that it does currently (give the appropriate incrementals are available). Is that correct? > > You're saying you don't think that's possible. Do you mean that it's > impossible in Bacula or impossible in general? Is it the creation of a > decremental backup or the creation of one from two existing full backups > that you see as the problem? If my understanding of what you are proposing is correct, then yes, I think it is possible. The next questions are: is it something we want to implemement? how big of a project is it? who would implement it? when? I don't have any answer for the above, except I imagine that it is not at all a small project. > > Looking at Wikipedia, it would appear that the term "reverse incremental" > is in use by someone already to describe something similar. > > http://en.wikipedia.org/wiki/Incremental_backup#Reverse_incremental > > Perhaps all of this is academic, but I think there probably are people who > would benefit from it. > Regards, Kern ------------------------------------------------------------------------------ Let Crystal Reports handle the reporting - Free Crystal Reports 2008 30-Day trial. Simplify your report design, integration and deployment - and focus on what you do best, core application coding. Discover what's new with Crystal Reports now. http://p.sf.net/sfu/bobj-july _______________________________________________ Bacula-devel mailing list Bacula-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/bacula-devel
