Re: [gentoo-user] rsync + tar + bz2 ?

[Grant <emailgrant@gmail.com>]

>> I'm backing up numerous large files on another machine on my local
>> network.  I've only been using rsync, but it occured to me that I
>> might be able to save some time and space if I incorporate tar and
>> bzip2.  How will rsync interact with those?  If I turn the whole
>> backup into a big tar.bz2, would rsync need to redownload the whole
>> thing if I change one file?  If so, maybe I should turn different
>> groups of files into tar.bz2 archives so rsync only needs to
>> redownload an archive if one of its files has changed?
>
> It's not a default behavior, but there is an '--inplace' option.
>
> Also,there is a '--compress' option, if the bandwith is the only
> problem, otherwise you can use lzma (with normal-best ratio) to either
> acheive much better compression than bzip2 or still slightly better
> ratio with improved speed / less cpu time with 'lzma -1' (fast mode).
>
> And if you're going to put a lot of files (like whole fs) into a
> single tar just to transfer it to some remote destination, prehaps you
> shouldn't be using rsync at all, since you'll end up reading all the
> files anyway to create the tar.
> Alternatively, you can save disk space on the source machine by piping
> tar directly to destination, with compression either on the source to
> lessen the banwidth, or on the remote to lessen the load on the source
> machine cpu.
>
> That said, you can also use tar to create (or pipe) incremental backups
> - just the changes since the time last one was made. Tar can handle that
> as easily as rsync does, since it checks what needs to be transferred
> each time anyway.
>
> --
> Mike Kazantsev // fraggod.net

Good stuff, thanks a lot Mike.

- Grant