Vista Tutorial - Excessive svchost reading of large files. What's going on?

Usually several times a day the reliability and performance monitor in Vista x64 shows an svchost.exe process extremely busy reading a particular file on my hard disk, and it usually keeps at it for at least five minutes, but sometimes closer to ten.

The files in question usually seem to be very large ones - just before I wrote this it was trashing around on a 4 GB video file I had just downloaded (I decided to try moving it to my external disk, the reading stopped instantly, as expected I guess).
Other times I've noticed the files have been 800 MB -1.5 GB+ game data files from eg. Fallout 3 or The Witcher.

Is there any way to find out exactly what that svchost process might be doing with those files?
My best guess would be something like the active file monitoring in Nod32, but that hardly explains why we're only talking about a select few, large files, and why it needs to take several minutes to do whatever it is that svchost process is doing to them (and it's only reading, not writing).

Excellent question.
What the hell is svchost.exe for anyway?
Ok maestros, now's your turn
*starts whistling*

Hello guys,

This is a pretty good article that helps explain what svchost.exe is for.

What is svchost.exe And Why Is It Running? :: the How-To Geek

Hope this helps,
Shawn

Thanks for the link. It looks like either Process Explorer or the tasklist /SVC command might be able to help me pinpoint which service is running behind that svchost process.
I'll give it a try the next time it decides to start its excessive file reading .

You're welcome Miths. I hope that you can get it tracked down.

It looks like these are the services hiding behind that svchost process:

svchost.exe 980 AudioEndpointBuilder, EMDMgmt, hidserv,
Netman, PcaSvc, SysMain,
TabletInputService, TrkWks, UxSms,
WdiSystemHost, Wlansvc, WPDBusEnum, wudfsvc

After a bit of research with help from Google, it looks to me like SysMain aka SuperFetch is the most likely culprit.
As I mentioned it seems to have been chewing a lot on particularly those large game data files (now I've noticed that the same goes for a lot of smaller ones as well, I just never really noticed those before as they obviously don't result in 5-10 minutes of hard disk trashing), and I guess that makes sense as I've been playing those games a lot the last few days, making those files prime candidates for whatever kind of optimization it is SuperFetch does.

Well, I guess at most half an hour of wild hard disk trashing a day is well worth listening to, if SuperFetch actually provides a noticable performance increase?
Anyone running Vista with SuperFetch disabled? I've got 8 GB RAM - not sure if that makes the service less useful than on systems with less memory?

Edit: Sounds like turning it off could actually be a good thing according to some of the comments on this page - http://www.howtogeek.com/howto/windo...windows-vista/
I'll give it a shot, but obviously any additional input on this topic is welcome.

Miths,

Superfetch helps to optimize your computer by trying to predict what files or data you will need and have that loaded in RAM waiting for when you do to speed things up. Over time, as it learns, it gets better at having what you need ready. The only thing having more RAM will help is that SuperFetch will be able to have more loaded and ready for you.

Well, judging by most of the comments on that article I linked to, it isn't exactly very adept at learning, and those long, intensive disk trashing sessions can be more than a little annoying.
I've turned it off now, so I guess I'll find out soon enough if that has a negative or positive impact on performance. But at least with SuperFetch and System Restore both disabled now, my ears will get some rest . When hard at work, the disk is by far the most noisy component in my new computer.

I look forward to hearing your results.

Well, the results so far - after a very PC intensive day with graphics work, web browsing, video playback and gaming (Fallout 3 and Age of Conan, the latter shut down and restarted numerous times as I've been testing out DX9 and DX10 differences) - is that there has been delightfully little noise from the hard disk, compared to the previous five days I've had this PC (the first three or four with both SuperFetch and System Restore enabled, which was just horrible).
If there are any performance differences between having SuperFetch enabled and disabled, they are so slight I haven't noticed them yet, and doubt I ever would.