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.
I was having the same problem but caused by a different issue. I did not realize there was a separate driver for RAID/AHCI, and when I switched from RAID back to AHCI on my machine (win7) the iastordatasvc started constantly using 30% of my cpu usage. I installed the AHCI driver overtop the old one and it solved my issue.
Justin_Mason has the answer. This fixed my issue.
I've installed a SSD RAID before I formatted and installed Windows. I used the stock Intel Rapid Storage driver off my mobo CD. My IAStorDataSvc was taking up 30% of my CPU at any given moment. I didn't know that there is a Intel Rapid Storage RAID driver. Now things are snappy and games are loading quicker (especially GTA 5).
Get the most up to date RAID version here: