rsync and moving files [Re: backup w/ snapshots]

[Greg Barniskis]

Svein Halvor Halvorsen wrote:

> But: If I move the file from /foo/test to /bar/test on my main computer, 
> rsync will create a BRAND NEW FILE in /bar (and delete the file in /foo, 
> since I used the --delete option). Now this NEW file will have a new 
> inode, and cover new sectors on disk. The snapshot will then tak 
> considerable more diskspace. If I move a large directory tree this way, 
> this will occupy huge amounts of diskspace.

Eh? Bad assumptions about snapshots, I think. If a snapshot occupied 
even a tenth of the space of the data that it represented, we would 
quickly fill all our disks and the snapshot technology would be 
almost as painful as useful.

A snapshot is essentially only an index of occupied disk space, not 
a copy of the actual data, and a snapshot is therefore much, much, 
much, much smaller than the data files that have changed. Read the 
relevant man pages and handbook sections again, and test your 
assumptions by measuring the actual change in snapshot size. I don't 
think your perceived problem really exists.


-- 
Greg Barniskis, Computer Systems Integrator
South Central Library System (SCLS)
Library Interchange Network (LINK)
<gregb at scls.lib.wi.us>, (608) 266-6348