**The Situation:**  

I want to copy a directory recursively to an external hard drive. The directory contains a lot of files (at least 100,000). 

**The Problem:**  

External hard drives tend to get quite hot when heavily used like in my task (usage over several hours). That is bad for the life expectancy. So since time is not an issue in my case I would like that the copying would take some rest between copying the files to allow the drive to cool down a bit.

At the moment I use `ionice -c3 nice nice cp -r` which at least reduced performance loss to all other running tasks. But it does not address the heat problem.

Any suggestions?

Using other commands than `cp` like `rsync` would be ok to (if applicable from command line) but so far I could not find any command or option that allows me to wait x seconds between each file copy.

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**Additional Information:**
The external hard drive is the final destination of the data not a way to transfer the data to another computer.