[plug] Constant rsync'ing...

[James Devenish]

In message <200303131704.33546.T.Phillips at murdoch.edu.au>
on Thu, Mar 13, 2003 at 05:04:33PM +0800, Trevor Phillips wrote:
> Is there a better solution? Ideally, something daemon-ish, that 
> auto-replicated changes, triggered by the filesystem itself? Or at least a 
> more efficient way of finding recently modified files? (I'd rather not rely 
> on datestamp - and it also needs to handle replicating file deletes...)

If you ask a question like "triggered by the filesystem itself" without
describing what operating system, hardware platform, and filesystem you
are using then you are surely indicating to us that you want answers
about the Linux/i386/ext2 combination. I don't know about that.

Firstly, a compromise: without having this feature in a filesystem, I
imagine that you'll have to settle for EITHER foolproof file matching
OR speedy matching.

In the case of the latter, I will *again* mention that Unison fits this
bill. In fact, I imagine it can do the former if you disable 'fastcheck'
(but obviously that means it has to compare file contents on both
machines and that would be slow). Fastcheck could potentially overlook
changes (unlikely unless you actually set out to thwarte it), though it
always does a 'safe check' before overwriting any files with supposed
"new" versions.

The first time you run unison, it will think for a long time, use your
disk, and use up some memory (doing initial directory comparisons and
recording state). But, thereafter, it is fast when there are no changed
files (or even if there are). Whether it amounts to a performance hit
for YOU, I don't know (never noticed it myself but I haven't had a need
for it on our most demanding user disks lately). The documentation
describes the ways in which differences are assessed speedily. It
handles deletions and can handle moves. You can run it in batch mode so
that it thinks for itself. It will not corrupt your data if there are
conflicts or power failures. &c.