Robin Lee Powell
2022-Jul-15 06:57 UTC
do I always have to use either --checksum or --times ?
--checksum is only slower than re-copying if your network connection between the hosts is similar in speed (or faster than) each host's local disk access. If local disk access is 10x your network link, it is definitely not slower than re-copying. Having said that, it really is *very* slow, and before you use it you should have a clear situation in mind that makes it plausible that two files could have the same size and last mod time and still not have the same data. Or, alternately, be in a situation where a bit flip would be catastrophic. Such situations are not common. On Thu, Jul 14, 2022 at 04:26:48AM -0400, Kevin Korb via rsync wrote:> You should almost never use --checksum. It is slower than just re-copying > everything. You should almost always use --times (or --archive which > includes --times). Without this rsync is almost as dumb as cp. Also, ssh > has been the default --ssh for a long time. > > On 7/14/22 04:22, Fourhundred Thecat via rsync wrote: > > Hello, > > > > I want to sync local folder to remote server. When I run follwing > > command repeatedly, it always transfers everything each time again and > > again: > > > > ? rsync --rsh='ssh' foo/ server:/foo/ > > > > does it mean I have to always use either --checksum or --times, to > > prevent repeated transfer of files that have not changed ? > > > > thank you, > > > > -- > ~*-,._.,-*~'`^`'~*-,._.,-*~'`^`'~*-,._.,-*~'`^`'~*-,._.,-*~'`^`'~*-,._., > Kevin Korb Phone: (407) 252-6853 > Systems Administrator Internet: > FutureQuest, Inc. Kevin at FutureQuest.net (work) > Orlando, Florida kmk at sanitarium.net (personal) > Web page: https://sanitarium.net/ > PGP public key available on web site. > ~*-,._.,-*~'`^`'~*-,._.,-*~'`^`'~*-,._.,-*~'`^`'~*-,._.,-*~'`^`'~*-,._., > > -- > Please use reply-all for most replies to avoid omitting the mailing list. > To unsubscribe or change options: https://lists.samba.org/mailman/listinfo/rsync > Before posting, read: http://www.catb.org/~esr/faqs/smart-questions.html
Yeah, unfortunately rsync's --checksum doesn't even employ obvious optimizations that the man page says it does. There is no reason for it to checksum files that only exist on one end or are different in sizes yet it does. Just try doing an rsync of a huge tree to an empty dir. You won't run out of space. You will get tired of waiting for it to do something and abort it. On 7/15/22 02:57, Robin Lee Powell wrote:> --checksum is only slower than re-copying if your network connection > between the hosts is similar in speed (or faster than) each host's > local disk access. > > If local disk access is 10x your network link, it is definitely not > slower than re-copying. > > Having said that, it really is *very* slow, and before you use it > you should have a clear situation in mind that makes it plausible that > two files could have the same size and last mod time and still not > have the same data. > > Or, alternately, be in a situation where a bit flip would be > catastrophic. Such situations are not common. > > On Thu, Jul 14, 2022 at 04:26:48AM -0400, Kevin Korb via rsync wrote: >> You should almost never use --checksum. It is slower than just re-copying >> everything. You should almost always use --times (or --archive which >> includes --times). Without this rsync is almost as dumb as cp. Also, ssh >> has been the default --ssh for a long time. >> >> On 7/14/22 04:22, Fourhundred Thecat via rsync wrote: >>> Hello, >>> >>> I want to sync local folder to remote server. When I run follwing >>> command repeatedly, it always transfers everything each time again and >>> again: >>> >>> ? rsync --rsh='ssh' foo/ server:/foo/ >>> >>> does it mean I have to always use either --checksum or --times, to >>> prevent repeated transfer of files that have not changed ? >>> >>> thank you, >>> >> >> -- >> ~*-,._.,-*~'`^`'~*-,._.,-*~'`^`'~*-,._.,-*~'`^`'~*-,._.,-*~'`^`'~*-,._., >> Kevin Korb Phone: (407) 252-6853 >> Systems Administrator Internet: >> FutureQuest, Inc. Kevin at FutureQuest.net (work) >> Orlando, Florida kmk at sanitarium.net (personal) >> Web page: https://sanitarium.net/ >> PGP public key available on web site. >> ~*-,._.,-*~'`^`'~*-,._.,-*~'`^`'~*-,._.,-*~'`^`'~*-,._.,-*~'`^`'~*-,._., >> >> -- >> Please use reply-all for most replies to avoid omitting the mailing list. >> To unsubscribe or change options: https://lists.samba.org/mailman/listinfo/rsync >> Before posting, read: http://www.catb.org/~esr/faqs/smart-questions.html-- ~*-,._.,-*~'`^`'~*-,._.,-*~'`^`'~*-,._.,-*~'`^`'~*-,._.,-*~'`^`'~*-,._., Kevin Korb Phone: (407) 252-6853 Systems Administrator Internet: FutureQuest, Inc. Kevin at FutureQuest.net (work) Orlando, Florida kmk at sanitarium.net (personal) Web page: https://sanitarium.net/ PGP public key available on web site. ~*-,._.,-*~'`^`'~*-,._.,-*~'`^`'~*-,._.,-*~'`^`'~*-,._.,-*~'`^`'~*-,._.,