External USB slows entire rMBP down?

[JefferyShin]

I hope this is the right place for this post.

I was exporting a video on Final Cut Pro X on my rMBP, and the 7 minute video took just under a minute to export at 720p, 24fps.

After exporting, I plugged in an external (portable) hard drive to transfer some file, and after it finished, I didn't eject it, and just let it sit there. Then I realized that I had to make a small change to the video (moving a clip), so I did that and exported again, but this time, it was taking about 10 minutes to export.

I wasn't sure what the issue was, and I checked Activity Monitor and there wasn't any other process that was hogging the CPU. During the 10-minute long export, I ejected the external, and it instantly sped up and finished in less than a minute.

I guess it's not much of an issue as I know now to eject things before exporting, but is this a normal issue?

Thanks.

 

[bobr1952]

If something was hogging your CPU it should have been shown in Activity Monitor--be sure you check all processes not just your user processes. I do notice that sometimes unmounting a drive can hog the CPU but that shows up in Activity Monitor.

 

[alphaod]

USB does require CPU usage. That's why Firewire was a good; it didn't require any intervention from the host.