On Thu, Feb 24, 2005 at 04:01:52PM -0800, Richard Patterson wrote: > Hello, > > Andrew Trigdell's original rsync paper (actually > thesis) discussed the idea of using rsync to make > incremental tape backups based not on whole files but > rather parts of files. Sadly, this functionality is > not actually present in the rsync program. I'd like to > explore adding this ability. > > There are basically three things that need to be done > to enable efficient (partial-file) incremental tape > backups, namely: > 1) Generation of rsync signatures from existing files. > 2) Generation of a binary patch from existing files + > an rsync signature. > 3) Application of a binary patch to existing files. > > Rsync already has the facility to generate and apply > binary patches -- namely, batch-mode operation. Thus > all that remains to be added is read and write support > for signatures. > > It seems to me the best way is through two new > options: --read-signature and --write-signature. > --read-signature would operate similarly to > --compare-dest. --write-signature would generate > signature files from the destination. > > Finally, one would need to be able to run rsync > without an actual destination parameter when used with > --write-batch. Thus we would have the following > combinations: > For a full backup: > --write-batch --write-signature > For a differential backup: > --write-batch --read-signature --write-sigature > For a leaf incremental backup: > --write-batch --read-signature > For a restore, one would specify --read-batch with no > source. > > I'm willing to implement this, but wanted to get some > feedback first. Comments?
Perhaps this would also be a useful optimization for server mode. During a period that the servers repository is not changing it could run from the signature file, which would effectively be a cache of the checksums. (as long as client didn't request a different checksum seed) Also, I think this might not be too hard to implement. Presumably, the signature file contains exactly what a "write-batch file" to an empty destination directory would contain, minus that actual file blocks. Is that what you're thinking? -chris -- To unsubscribe or change options: https://lists.samba.org/mailman/listinfo/rsync Before posting, read: http://www.catb.org/~esr/faqs/smart-questions.html
