If I use the "-I" to ignore date and size as quick-check methods of determining change, what method does it use to determine difference? If it falls back to checksumming the entire file, maybe the manpage might warn that this would be as expensive as using the "-c" option...or not depending on what it uses for determining difference at that point. So exactly how does rsync compare files for differences when date & size are used but checksumming is not? Thanks! -Linda
On Sun, Aug 01, 2004 at 06:20:11PM -0700, Linda A. W. wrote:> If I use the "-I" to ignore date and size as quick-check methods of > determiningjust modtime. rsync never ignores size differences.> change, what method does it use to determine difference? If it falls > back to > checksumming the entire file, maybe the manpage might warn that this > would be > as expensive as using the "-c" option...or not depending on what it uses for > determining difference at that point.Short answer: It does fall back to checksum comparison. Long answer: I'm not sure, but I suspect that the reason this is not so explicit in the man page is that it's a bit complicated in the code, too. I _think_ that using -I would be even more expensive than -c, because it will take longer to eventually do the same checksum comparison. But, Wayne knows these options like the back of his hand. Wayne? -chris> > So exactly how does rsync compare files for differences when date & size are > used but checksumming is not? > > Thanks! > -Linda > -- > To unsubscribe or change options: > http://lists.samba.org/mailman/listinfo/rsync > Before posting, read: http://www.catb.org/~esr/faqs/smart-questions.html
On Sun, Aug 01, 2004 at 06:20:11PM -0700, Linda A. W. wrote:> If I use the "-I" to ignore date and size as quick-check methods of > determining change, what method does it use to determine difference?With -I, rsync does no advance determination of sameness, it just transfers all the files and lets the matching data make the transfer as small as possible. This is more expensive than -c if all the files are the same (since the receiving side reads the file twice and writes it once for each file), but could be slightly faster than -c if most of the files have changes (since the -c option makes the receiving side read the file thrice and write it once when it is different, but only reads the file once if it is the same).> So exactly how does rsync compare files for differences when date & > size are used but checksumming is not?When date & size are used, rsync skips the file when the modify time and the size is identical on the receiver and the sender for a given file. ..wayne..
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