There are just a couple people here that are really knowledgable about Server so I hope they'll chime in. I do know that the more RAM you can give your server the better! I seriously doubt that only part of an extract would be loaded into RAM but I won't swear by it.
What is your operating system? How many cores? How much RAM? How much available hard drive space?
Also, why are your extracts so large? The extract should only have the needed data for the report and nothing more. Hide fields not being used, filter the data down (for example, a WHERE clause if using Custom SQL), etc.
Okay, let's get your thread to a location so that others can see it. Click on the "Move" link on the right side of your screen:
Next, click "Spaces" and then "Forums":
Click the orange button that shows up in the next pop-up and your thread will get moved to more eye-*****
Don't worry, this wasn't directly your fault, the forum is just a little "special"
P.S. Thanks to Shawn Wallwork for pointing out this thread.