The toolbar icon (IAStorIcon.exe) and the display application it calls up (IAStorUI.exe) are a valuble interface to the Intel Rapid Storage Technology service (IAStorDataMgrSvc.exe). You don't need them but they are more useful than not. By the way, the reason you think something is not loading is because the service is set to automatic delayed start by default. I am not sure why it needs to be delayed but that is why you see the the exclamation point in the toolbar icon for a minute or so at bootup instead of the green checkmark. If you just ignore it it settles in once the service finishes loading. If you really want to disable the user interface part of RST you have enough info now to do so.
Why shouldn't I simply disable the iastordatamgr service, and not startup the tray icon program?
That will save a little memory and boot time.
I would like to make my system as light as possible.
I don't see what this software brings me while I have a laptop with only one drive.
Firstly Intel sugest you run the Rapid Storage Technology software on your PC. One advantage is that it will report any hard drive errors and let you know quickly what the features your hard drive currently has e.g. whether it's using Native Command Queing or whether Disk Data Cache is enabled.
I would suggest you leave it on your OS as it has a low 'footprint' not taking much resources up. I set the Intel Rapid Technology Service to Automatic using the 'services.msc' command. This makes it start quickly and avoids the annoying icon on the Windows Taskbar if you leave it at 'Automatic delayed start.' If you want to stop programs running automatically go to the Windows start icon, type msconfig, then click the 'Startup' tab, then untick each program you don't want Windows to automatically start. I only let my antivirus, Intel Rapid Storage Technology and my Catalyst Control Centre graphics control program start. You will probably see a lot of auto start programs such as Adobe, iTunes, Quick time, keyboard, mouse and webcam programs auto starting. You can untick all these as this won't stop the program working if you ever need to open it and it will save resources. Remember only do this if you research the pros and cons of stopping the items currently starting up. You should check the msconfig startup items every time you install updates to software as they often appear back on the startup items once you update programs like iTunes or Adobe Reader.
I'm running 10.10.1008 Intel Rapid Storage Technology as I think this is the most up to date version?