This is referring to the matter stated here and I am also experiencing the same.
In one of my servers, I ran an rsync, to backup a huge directory (size greater than 300 Gb) to a different disk, mounted on same machine. The directory being rsynced contains thousands of directories and files. I issued a single rsync command, with 'nohup' and then pushed it in background using the '&' command. The complete command given on the remote bash shell (using putty) was:
nohup rsync -avh /some/local/dir /backup/ >> /opt/rsync.dec22.log &
Then just to check at what rate was the data being copied, I used 'iotop' command, and found that there were 3 rsync running with same parameters. On searching I found the link above which says that it is normal.
But doing an iotop to monitor only those and the only rsync processes running on the system, I see that one process is reading files, one is writing them, but one is idle. The behaviour seems to be good, as one process doing only one thing at a time, but what is the 3rd process doing (seen as the middle one in the image below)?
The iotop command I had used was:
iotop -p22250 -p22251 -p22252
Here is the screenshot for the iotop command output:
I am asking this cause I use rsync a lot, and want to understand its behaviour for long term benefit. I even read the manual, but it says nothing of the forking.