Hi papadiva,
I would suggest you to install the latest Intel Rapid Storage compatible for Windows* 8.1, this will be version 12.8 and check if “Iastordatasvc” takes a lot of resources from your computer
Here is the link for the latest version: File name: SetupRST.exe
To answer your questions: This service monitors the data transfer on your computer and this is part of Intel Rapid Storage software, it should be active all the time, I am afraid since Intel does not handle removing or deleting services or files, I am afraid I am not familiar with the behavior of the application. Try updating to the latest version compatible for your operating system version.
Thanks
Allan