[Dirvish] Beginners questions

[rboulle at free.fr]

Hello,

Thanks for your reply.

Selon Jon Radel <jon at radel.com>:

> Rémi Boulle wrote:

> > For what I understood dirvish write only the changed parts of the
> > changed files.
>
> While, if backing up across the network, rsync transfers only the
> changed portions of changed files, what is written to disk is the entire
> changed file.

Ok, so dirvish "just" add the part sent by rsync with the unchanged part already
on the hard drive ?

> > My first image is roughly 5 Go, so why the second one is 5Go too ? (no
> > files were changed)
>
> How did you measure this?

Right click/properties ;-) (on ubuntu)

>If you simply ran du against each image, then
> yes, they would both show as 5 gig.  However, if you run du against both
> images at the same time, it should still show about 5 gig and not 10
> gig.

So individually they use 5 gig each and globally they use 5gig + epsilon ?

> Each image is equal, in the sense that no image is the "full
> backup" and other images are the "differential backup."  They're all
> "full," some were just made earlier, but there is only one copy of each
> unchanged, unmoved file physically taking up blocks on the hard drive.

Ok, so eg the second image as a 5 gig space *reserved* on the filesystem (but
not used).

> This all assuming that you've not made any configuration errors, or run
> dirvish with the --init option more than once, or changed critical
> configuration choices between backups.  It *is* possible to create
> backups that have no link with each other.  (Which many of us do
> deliberately for extra safety.

>From a disk space point of view it is totally equal no ? The only difference is
from network load point of view...

Am I right ? :-)

Hum, so, is it possible to make differential backups everyday day and, once a
month, a total backup (I mean with no link) ?

> > Does it mean that all those images are "real" images ? eg I can delete
> > last monday image without having any problems ?
> >
>
> Unless you want to restore a file that was captured only in that backup.
>  :-)  If you delete the last successful backup, you'll have to run
> dirvish with the --init option again.  Other than that, you can delete
> any image without an issue.

So the "mustn't to be touched" backups are the first one and the last one ?
Thanks a lot.
Things are getting clearer for me.
Cheers.
Rémi.

>
> --Jon Radel
>