Re: [rdiff-backup-users] Re: offsite service providers?

[Greg Freemyer]

On 3/16/07, Dimi Paun <address@hidden> wrote:
> On Fri, March 16, 2007 17:29, Greg Freemyer wrote:
> > That is sounding fairly safe and reasonably bandwidth efficient.
>
> That's true, if you don't have large files that change in incremental
> ways. The encrytion _should_ render these useless for differential upload.
> In fact, that mey be the case even for files that don't change, depending
> on how EncFS works.

I'm not knowledgeable on EncFS, but I believe in general filesystems
that encrypt do it one block at a time in such a way to have the
encrypted block occupy exactly the same space on disk as the
unencrypted block would.

So assume it is a 4k block, then if you update any data in that block it must:
  read (4k block) - unencrypt - modify - encrypt - write (4k block).

Otherwise writes to the middle of the file would be highly inefficient.

So changes in the middle of a large file should not impact the rest of
file outside of the block you updated.  This should allow rsync to
work well.

Greg
--
Greg Freemyer
The Norcross Group
Forensics for the 21st Century