Why does MacOS file sharing take so much CPU? I’m rsyncing 30GB of files from one Mac to another. Using MacOS file sharing, 10.9.4 server and 10.9.2 client. The client is a MacBook Air and the fan is whirring away. Some kernel_task associated with the copy is taking 50% of one CPU; the rsync processes are taking another 13%. It’s not awful, but that’s a shitton of CPU for doing something that should be low impact. The iMac server is using 15% of a CPU to serve the files too.