The rsync method was developed as very fast initially. For now, it earns both worldwide acceptance and some end-user complains for relative slowness under some uncommon circumstances.
rsync is a program used by UNIX-like systems for data synchronizing.
This program has some key features, shortly described below:
rsync can be used as a utility or as a daemon, in which case it has a standard port nunbered 873.
As rsync is a native file-synchronizing tool, many backup solutions utilize the capability of it to effective mirror files as a main mean of backup data transfer.
This algorithm also has some native capabilities for generating delta files (just the same sort of things as produced by differential backup). Many modern utilities and programs are prepared for adequate rsync files generated by that software, thus severely speeding up the flow of mirrored data.
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