ccddtt wrote: >1\ rsync,is a good sync file tools. but i think is not for me question. >because: when i update some data to rrd file,the file is status is >'changed',so rsync need transfer the complete file .Is my analysis >correct?
No, you don't understand how rsync works. The main feature of rsync is it's ability to copy parts of a file. This makes it very efficient at updating files across a low bandwidth and/or high latency link (it parallelises operations to deal with high latency). See http://en.wikipedia.org/wiki/Rsync and also in particular see external link #7 http://samba.org/~tridge/phd_thesis.pdf which is Andrew Tridgell's thesis on sorting from which rsync sprang. Short version: He worked on an efficient process for sorting, and from that comes an efficient process for working out which bits of a file have changed - sorting and searching a list are somewhat related. The basis of the rsync protocol is : 1) use the part of the process to make fast (sheap) checksums of blocks of the file and compare them to file blocks that are different. 2) Use the efficient search process to find if blocks have moved rather than been changed. 3) Copy only what's needed to re-assemble the original file at the destination using what's already there in the previous version. While not applicable to your needs, rsync can even deal with a file where a small amount has been inserted or deleted (step 2 above). Eg if you add a single byte to the front of a 1GB file, then rsync will detect this and not copy the whole GB. It is worth reading the man page carefully, this compression isn't the default for all transfer modes, nor is encryption using the SSH protocol. -- Simon Hobson Visit http://www.magpiesnestpublishing.co.uk/ for books by acclaimed author Gladys Hobson. Novels - poetry - short stories - ideal as Christmas stocking fillers. Some available as e-books. _______________________________________________ rrd-users mailing list rrd-users@lists.oetiker.ch https://lists.oetiker.ch/cgi-bin/listinfo/rrd-users
