duplicity-team team mailing list archive

[Plamen Kosseff <p.kosseff@xxxxxxxxx>]

---------- Forwarded message ----------
From: Plamen Kosseff <p.kosseff@xxxxxxxxx>
Date: 2009/9/11
Subject: Re: [Duplicity-team] Auto Coalescing Incremental Backups
To: Kenneth Loafman <kenneth@xxxxxxxxxxx>


Hi,

If I'am willing to sacrifice the ability to revert to the state in inc1 and
it's bandwidth efficient (i.e. it is not over some configurable size) I will
prefer not to keep the incrementals at all and do an incremental against the
last full every time.
This will actually work better spacewise if you have very hot files which
changes are likely to be overwritten in later incrementals.

So it will look like this
  Full Backup has files ABCD and blocks a1..a23, b1..b5, c1, d1
  Inc1.0 Backup has files AC and blocks a4,a7,c1
  Inc1.1 Backup has files ACD and blocks a4,a7,a8,c1,d1  (inc1.0 is removed)
  Inc1.2 Backup has files ABCD and blocks a4,a7,a8,b3,c1,d1   (inc1.1 is
removed)
  ......



2009/9/11 Kenneth Loafman <kenneth@xxxxxxxxxxx>

Folks,
>
> This seems like a workable idea for coalescing incremental backups on
> the fly, without user intervention.
>
> A very simple case:
>   Full Backup has files ABCD and blocks a1..a23, b1..b5, c1, d1
>   Inc1 Backup has files AC and blocks a4,a7,c1
>   Inc2 Backup has files AD and blocks a4,a8,d1  (a4 has been replaced)
>   Inc3 Backup has files AB and blocks a7,b3     (a7 has been replaced)
>   Inc4 Backup has files CD and blocks c1,d1     (c1 has been replaced)
> At this point, all of Inc1 has been replaced, so if the user is willing
> to do so, Inc1 could be deleted.  We would have to fix up the chain in
> some manner so it would not be missed, but the idea seems workable.  I'm
> not sure how often this would occur in actual use, but I wanted to get
> the thought out there while I had it.
>
> The simplest solution is to coalesce Inc1..4 into one incremental, and
> that will probably the first solution we implement.
>
> ...Thanks,
> ...Ken
>
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