Thanks for reply. it will be ok that replistor will not re-send file that is already sent to target.
but how about if only one big file (say 10G) in source site, when 2G transferred to target, and link broken, in this scenario, what will be the next step when link resumed?
1) resend from scratch
2) continue send the remaing 8G data

If you re-sync after the interruption then RS will open the first 64KB of the 10GB file, create a CRC check sum of that first chunk of the file. It sends over the CRC check sum to the Target. The Target opens the same chunk of the 10GB file and creates its own CRC check sum number. It then compares the check sums and if they are the same, it assoums that chunk of the file is OK.

RS will run through the entire 10GB file in the same manner. If any of the chunks do not compare or if the chunk does not exist, RS will re-send the chunk of the files. It goes throught the whole file in that manner until all the chunks compare correctly. At that point, the files are the same on both nodes.