Mapped Drive

Stephen Zemlicka stevezemlicka at
Sun Sep 30 18:45:16 GMT 2007

OK, let's say this is the first sync and every file is being transferred.
The checksum for each of the files is cached on the local drive.  Then, the
next time you sync, it checks the checksum from the cache against the file
to be copied.  If it matches, it skips it.  If it doesn't match, it just
transfers just the difference.  It then replaces the checksum of that
transferred file to the cache.  That way one could have a remote data store
and not have to run rsync on the remote system.  IE, you could have a mapped
drive or FTP folder or S3 storage area that would all be rsyncable.

Stephen Zemlicka
Integrated Computer Technologies
PH. 608-558-5926
E-Mail stevezemlicka at 

-----Original Message-----
From: hashproduct at [mailto:hashproduct at] On Behalf Of Matt
Sent: Sunday, September 30, 2007 11:54 AM
To: Stephen Zemlicka
Cc: rsync at
Subject: Re: Mapped Drive

On 9/30/07, Stephen Zemlicka <stevezemlicka at> wrote:
> The problem is some files don't change in size.  So I was hoping that the
> checksums could be cached.  Perhaps I'm mistaken but I thought the
> determined what actual blocks were transferred.  I suppose it could be
> cached at either storage location.

I still do not understand what you are proposing; please be more
specific!  Which checksums are you talking about: (1) the whole-file
checksums of destination files used by the -c option to decide whether
to transfer each file, or (2) the block checksums of destination files
used by the delta-transfer algorithm to match blocks, or (3) something
else?  At what point in the process would the cache be read, and at
what point would it be updated?


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