-c Option

tim.conway at philips.com tim.conway at philips.com
Thu May 30 09:43:02 EST 2002

The only reason to use -c is if you have data which may be changed without 
changing mtime, ctime or size (is there any case where that happens?).  It 
makes rsync read EVERY file, from beginning to end, and generate a 
checksum for comparison.   If the size/time assumption is valid, it's a 
heck of an optimization, as you've noticed.

Tim Conway
tim.conway at philips.com
Philips Semiconductor - Longmont TC
1880 Industrial Circle, Suite D
Longmont, CO 80501
Available via SameTime Connect within Philips, n9hmg on AIM
perl -e 'print pack(nnnnnnnnnnnn, 
".\n" '
"There are some who call me.... Tim?"

Michael Montero <mmontero at mail.communityconnect.com>
Sent by: rsync-admin at lists.samba.org
05/30/2002 08:27 AM

        To:     rsync at lists.samba.org
        cc:     (bcc: Tim Conway/LMT/SC/PHILIPS)
        Subject:        -c Option

Hello all.  I've been using rsync for quite some time and when I
originally began using it I was religious about including the -c option.
I've read the man page and noticed the significant performance hit I take
in using it.  I was wondering if someone would be able to clarify for me
what the benefits are in using this option.  Why would someone want to?

I can't quite remember why I decided to use it....the scripts using rsync
were written nearly 3 years ago.  However, I must have read somewhere on a
mailing list that the option was important for one reason or another.

Any insight would be great.  I can cut my sync times down by almost 80%.


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