To a run a site as massive as Facebook inherently requires a massive infrastructure of data centers. The Web site’s IPO filing on Wednesday sheds some light on just how much it costs to maintain and construct such facilities.

According to the document, Facebook had $500 million in “non-cancelable contractual commitments as of December 31, 2011, primarily related to equipment and supplies for our data center operations, and to a lesser extent, construction of our data center sites.”

The paperwork also says that the company’s costs have increased each year and it expects going forward to have increased costs “in particular for servers, storage, power, and data centers, to support our anticipated future growth.”

Facebook says that last year it began using data centers that had been designed specifically on their behalf. (The first one, located in Prineville, Ore., began serving data last April). The company plans to keep growing its infrastructure primarily through the creation of its own custom data centers. With this move, the company says its expects to see an increase in energy efficiency and a decrease in operational costs. It’s easy to see why the company would want to cut costs in this area. The document shows that its current operational lease obligations total $2.2 billion.

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