Re: [Duplicity-talk] are periodic full backups necessary?

[Ian Barton]

> > Perhaps a single large "virtual" volume could be generated for a 
> > complete backup, would would then be used to apply the rsync algorithm 
> > to the previous volume. This assumes the rsync algorithm only requires 
> > one pass (does it?) and that it will all work well even in the face of 
> > large displacement of data in this huge file (probably not).
>
> OK, I must admit I never thought of that one :)
> I don't think it will play well with the encryption.
>
> > Anyone have better ideas?
>
> Another idea might be to use an encrypted virtual volume and to use hard 
> links in it, like some tools do.
> With hard links, it's pretty easy to implement backward diffs.
> And confidentiality is ensured, since it's only a huge file.

I used to do something like this using a Truecrypt container (no 
Duplicity involved). There were at least two problems:

You couldn't grow the container, so had to start off with whatever you 
thought the max container size you would need.

Using rsync to sync the local and remote copies was a problem. Since the 
TC container file size didn't change I needed to use an extra rsync 
switch which generated a checksum of the files so rsync could work out 
what had changed. With large containers (4GB) this was very slow.

At the moment I use Duplicity to save stuff to an external usb hard disk 
and then rsync that to my off site storage. it works well for me - if I 
go away for a few days I can simply unplug the usb drive and I have an 
encrypted copy of all my data with me.

Ian.


Ian.