Reindl Harald wrote:
Am 19.01.2013 19:28, schrieb Nicolas Thierry-Mieg:
no I don't think you will, since the file modification times won't have changed.
and even if the did - who cares?
- rsync does not transfer unchanged data ever
- rsync will sync the times to them from the sources
- so have nearly zero network traffic
Not true: if you change the modification time on a file, by default rsync will copy the whole file again.
See man rsync: Rsync finds files that need to be transferred using a “quick check” algorithm (by default) that looks for files that have changed in size or in last-modified time.
and yes I've tested this before posting ;-) to avoid this you need to use --size-only
bullshit
yes it transfers - but with rsync algorithm RTFM how rsync works - it will generate checksums on both sides, tnrafser only the checksums and come to the conclusion that the data are ident
i am using rsync since many years for all sort of backups and file transfers and even my thunderbird-profiles over WAN is copied with a "virtual speed" of 200 Megabytes per second ________________________________
[harry@srv-rhsoft:~]$ ls /mnt/data/profiles/thunderbird/harry/global-messages-db.sqlite -rw-r----- 1 harry verwaltung 640M 2013-01-19 19:31 /mnt/data/profiles/thunderbird/harry/global-messages-db.sqlite
this file will ALWAYS be changed, not only modification times but that does not change the facht 99.8% of the file is unchanged and rsync by design transfers only the changes over the wire
since i am doing this DAILY between home and office machine you do not need to explain me how rsync works and in which cases in trafsers data - really you do not need
i sync some TB of data daily inclduing GB large logfiles where is also only the new part transferred all the time
woosh! chill out dude...
again, read the man page. This is not true if source and dest are local: then the rsync algo is not used, and if the mod time is changed on the source the whole file will be copied. so if you're rsyncing locally, eg to a usb drive, you need --size-only as I said.
Now if one of the source or dest is remote I agree with you, but this is not alwayss the case. I don't recall whether the OP expressed whether that was the case or not, though I think he mentioned wanting to backup family pictures, so it might very well be to a usb HD. Inany case I definitely know you mentioned testing things locally. Which I did, and you didn't...
being wrong is ok, but you should really work on that attitude of yours.
On Sat, Jan 19, 2013 20:29:02 PM +0100, Nicolas Thierry-Mieg wrote:
I don't recall whether the OP expressed whether that was the case or not, though I think he mentioned wanting to backup family pictures, so it might very well be to a usb HD.
I am the OP. I explicitly made the example of one big album of family pictures because it was my own most recent experience of the problem I wanted to discuss. I backup more or less regularly those pictures and other stuff to both local drives (external USB) AND to remote computers through the Internet. Since I had seen the SAME behavior in both cases, I unconsciously assumed that it was not relevant, and didn't provide details.
being wrong is ok, but you should really work on that attitude of yours.
Indeed. Thanks Nicolas for pointing that out.
Reindl, you are very competent. There is no doubt about that. My current rsync scripts work better than their previous version also thanks to explanations from YOU (and others) in older threads on this or other mailing lists, and I thank you sincerely for that.
But the regular tone of your answers makes me wonder if those many GBytes you backup daily... you have to carry them on your back, one bit at a time.
I am not a novice, and I am not afraid to do my homework, quite the contrary actually. Besides, while not being Torvalds by orders of magnitude, I do enough work about Linux and FOSS in public that it would really be against my own professional interest not to do it on public lists.
In this occasion I did not "test locally" simply because, believe it or not, the feedback and tone of the thread up to that moment made me think that it would have been more interesting and productive for THE LIST to brainstorm togeteher on these less known parts of rsync. Which, if I look at ALL the replies I got (including yours) minus YOUR outburst, is more or less what actually happened.
So yes, Reindl, please do chill out, we need you. To the list: I owned the whole list a reply because I am the one who triggered this flame, but please let's NO MORE argue about it, only about rsync quirks.
Ciao, Marco
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M. Fioretti -
Nicolas Thierry-Mieg