Does Duplicity check the validity of previous incrementals?

On 22.08.2012 06:30, justink wrote:
> New question #206477 on Duplicity:
> https://answers.launchpad.net/duplicity/+question/206477
>
> Hi Guys
>
> Just wonder does Duplicity check the validity of previous incrementals before doing an incremental?

no

>
> Assuming I did 1 full backup, then 10 incrementals
> - Would the 11th incremental check that the first full and next 10 incrementals are all valid and OK before proceeding?

no

>
> note:
> * i read something abotu signatures in the man pages but not sure if that checks if the file is fine and restorable - or just it exists

exist for /verify/ runs, which you have to run explicitly

> * also hope support for amazon glacier comes to duplicity!
>

you might want to start a feature request on
https://bugs.launchpad.net/duplicity
headed 'Feature Request:'.
don't expect too much, the manpower behind duplicity currently sparsely adds up to one quarter of one sparetime manpower out of three regular contributors.

..ede/duply.net

thanks for the clarification ede!!

cheers

justin

a little clarification on why does not do this every time.

verification is an expensive process (bandwidth,cpu cycles) with duplicity. because of the 'dumb backend' paradigm the verification has happen locally. this means:

- mapping the file to verify to the remote volumes it is contained in
- downloading each of it and creating the file in tmp space
- downloading incrementals to patch it to state at the time stamp that needs to be verified
- compare it to the saved checksum

this is repeated for all files to be verified. essentially it is a restore that discards the files after checksum comparison.
i am not sure if duplicity repeats a volume download if it was already downloaded during the same run though.

..ede/duply.net

thanks!

question: does duplicity check that previous incrementals exist at all before a new incremental ?
-- assume we are not talking about the actual validity of the incremental

cheers

justin

On 23.08.2012 22:16, justink wrote:
> Question #206477 on Duplicity changed:
> https://answers.launchpad.net/duplicity/+question/206477
>
> Status: Solved => Open
>
> justink is still having a problem:
> thanks!
>
> question: does duplicity check that previous incrementals exist at all before a new incremental ?
> -- assume we are not talking about the actual validity of the incremental
>

actually this doesn't matter. fulls are just incrementals that assume the whole file changed. the new incremental collects the most recent rolling checksums (rsync algorithm) needed from the chain and backs up changed checksums.

why are you asking? ..ede/duply.net

thanks ede

why?
- used to admin veritas enterprise edition and 1 messed up incremental could ruin your restor

just want to understand more about how duplicity actually works - so i dont have to worry backups wont restore

cheers

justin