Re: [rdiff-backup-users] Updating mirror more often than incremental backups?

[Patrick Nagel]

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Hi Randy,

Randy Orrison wrote:
> I suppose this is a strange request.  I used to use rsync to create and
> update a mirror of my /home directory (on /backup/home, where /backup is an
> external USB drive).  This is my home PC, used just by my family, so
> updating the mirror only takes a few minutes, and I've had cron running it
> every hour.  I've just switched over to rdiff-backup, which is working like
> a charm.  However...I like the idea of having the mirror as up-to-date as
> possible, but really don't need the hourly incremental history.  Is there
> any way to update the mirror (in /backup/home) on an hourly basis, but only
> create incremental backups daily?
> 
> I have come up with a way to do it, but it's a bit ... hacky.
>     rdiff-backup /home to /backup/home.rdiff, daily
>     rsync --link-dest=/backup/home.rdiff /home /backup/home.rsync, hourly
> If I'm right about how things work, that'll give me a rdiff-backup mirror in
> /backup/home.rdiff with daily incremental backup history, and a mirror in
> /backup/home.rsync that's updated hourly, and any files that are identical
> between the daily and hourly mirrors will be hard-linked so as not to waste
> space.

Sounds like a good solution to me :)

> Does that sound right, and is there an easier way? It would be nice to be
> able to run rdiff-backup hourly, with a parameter telling it to only
> generate incremental history daily.

I'm just a user and don't really have a clue - but from what I know how
rdiff-backup works, this is impossible. It stores *reverse* diffs - so if the
mirror changes, the newest diff doesn't "cleanly apply" anymore to the mirror,
and is thus useless. And so are all the other diffs... So basically you would
have to store the mirror twice - once as a base for the diffs, and once as the
more-often-changing non-versioned mirror. Which comes down to your solution ;)
Ok, maybe this could be implemented as a function into rdiff-backup directly -
but anyway it's not hard to do it just as you did.

Patrick.

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