I started running
rsync in three programs at the same time to transfer data between my external hard drive and my internal one. When they finished, I have their timing results:
$ time rsync -a /media/t/1/ ./ real 236m14.131s user 22m57.025s sys 12m35.219s $ time rsync -a /media/t/2/ ./ real 106m45.245s user 3m6.938s sys 1m25.902s $ time rsync -a /media/t/3/ ./ real 55m48.494s user 2m6.053s sys 0m52.557s
Is the big difference between real and user+sys mainly because
rsync perform mostly IO operations between my external and internal hard drives, and the IO operations are not run in cpu but in DMA or the controllers of the two hard drives, and thus do not count into either user or sys times?
rsyncprocess is probably multithreaded, which increase user+sys time.
at the first half of the time, the three programs run at the same time, competing each other for IO? That may contribute a lot to the real time?
The first program transferred 108GB, the second 17GB and the third 12 GB.
my OS is 64-bit Ubuntu 14.04, and my computer is Thinkpad T400.