Los Angeles-based online advertising technology firm OpenX has opened up its fifth data center, the company announced this morning, to help support its online advertising marketplace. OpenX said the new data center will be located in Chicago, and comes on top of its existing data centers in LOs Angeles, Virginia, Amsterdam, and Tokyo. OpenX said the data center is the first new data center in a major expansion for the firm, and that it expects to open four, additional data centers by the end of 2013. OpenX provides online software used by content publishers to handle advertising serving and also for real-time bidding for ad placements on sites. The firm is venture backed by Accel Partners, Index Ventures and SAP Ventures.