[OpenAFS] fine-grained incrementals?

[Sergio Gelato]

* John S. Bucy [2005-01-31 16:14:59 -0500]:
> I'd like to use something like the following as a way to get
> fine-grained incrementals/versioning of volumes; the mtime-based
> incremental dumps presumably have to dump a whole file even if you
> only change 1 byte.
> 
> I'm thinking of the following protocol:
> 
> 1. take a full volume dump daily

Unless you're working on the file server, this could generate a lot more
network traffic than doing the incrementals. In any case, it will generate
more disk I/O.

> 2. use a (smart) binary diff system like rdiff (xdelta3?)
> to generate a delta from the previous day's full dump
> 3.  delete the previous day's dump.
> 
> It seems like the dumps would have to (at a minimum) have all of the
> objects appear in the same order every time for this to work reasonably.

Yes, that could be a problem too (but will mostly affect the size of your
binary diffs, not the correctness of the procedure). You could try it and see.

A diffing tool with knowledge of the dump format may be able to compensate 
for this, if it turns out to be a serious issue.

> Thoughts?

I've been glancing at rdiff-backup recently (along with a few other tools).
The main advantages of vos dump are that (a) it knows about AFS-specific
metadata like ACLs, and (b) it may be able to keep track of file renames
within a volume (although I haven't checked that it actually does). But
maybe, if one were given a tool to extract all AFS metadata from a volume, 
the rest could be handled with rdiff-backup's mechanism of computing xdeltas 
on individual files, not on the entire dumpset at once.