-----Original Message-----
From: Les Mikesell [mailto:lesmikesell AT gmail DOT com]
Sent: Wednesday, August 26, 2009 3:58 PM
To: General list for user discussion,questions and support
Subject: Re: [BackupPC-users] A Question on full backups
Nigel Kendrick wrote:
> Hi,
>
> I have had a read, but I am none the wiser...
>
> I understand that incremental backups are hard-linked delta copies based
> on the last full backup, but when a new full backup is performed, is
> this done as a complete new transfer, or are full backups also built
> from deltas of the last full backup and/or incrementals?
You need to separate the xfer method from the storage to understand this.
With
tar or smb methods, the entire contents of a full are transfered. With
rsync or
rsyncd, this is a delta against the previous full (or incrementals if using
levels) but if any content has changed in a file, a complete new copy is
reconstructed on the backuppc server side. Then, regardless of the method,
all
content that matches a file in the pool is discarded and replaced with a
hardlink - and all new/changed files have a new link added to the pool
(there
are no per-file deltas stored).
--
Les Mikesell
lesmikesell AT gmail DOT com
Thanks Les,
Yes, I meant this with reference to rsync/rsyncd.
Just going back to my previous query about SQL dumps and my daily backups
transferring the whole lot, I now realise that the last full backup was done
when the system was under test and I had not yet included the SQL dump
folder. The dump folder (700MB) was then picked up by the first incremental
and has been transferred ever since because, as I now know, same-level
incremental deltas are done against the last full backup and not between
incrementals.
If my understanding is correct, I presume I should then see a marked
reduction in the size of incrementals after the next full backup?
Nigel
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