Write only changed blocks to disk using rsync client only

Matthias Schniedermeyer ms at citd.de
Mon Nov 24 17:30:49 GMT 2008

On 24.11.2008 07:10, bjquinn wrote:
> I understand that if you want to only transfer changed blocks across the
> network that the remote machine must be running rsync server and the local
> machine must be running rsync client.  What if I don't care what gets
> transferred over the network, I just care what gets written to disk (i.e.
> only changed blocks)?  Is there an option to do that in rsync without
> needing an rsync server on the other end?
> I have an OpenSolaris server that I'm using for backups.  It's running ZFS,
> so if only part of a file changes, I can take a snapshot and be able to have
> access to both copies of the file but only store the differences.  However,
> if the entire file gets copied back down to disk, ZFS isn't smart enough to
> realize that the new blocks copied to disk are the same as the ones that
> just got overwritten - so it marks all blocks of the file as changed and
> doesn't provide any space-savings.  If rsync had a mode that made sure only
> to write to disk the blocks that changed, this would get me around this
> problem.  Also, since many of the computers I'll be backing up are Windows
> machines, I don't want to hog their CPU, and I don't care how much data gets
> transferred over the network, I'd rather avoid installing the rsync server
> on those machines.

reads like it is what you want.

Bis denn

Real Programmers consider "what you see is what you get" to be just as 
bad a concept in Text Editors as it is in women. No, the Real Programmer
wants a "you asked for it, you got it" text editor -- complicated, 
cryptic, powerful, unforgiving, dangerous.

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