On Wednesday, Rackspace said it had completed production load tests on generators, eliminating the problems behind the outage and returning the data center to "normal operating conditions."

Rackspace has a long history providing co-location services, and is making a run at the emerging cloud computing market with new services for hosting storage, virtual servers, and a Web application platform.

Several customers complained on the comment portion of Rackspace’s blog last week, with one person writing "your lack of redundancy for your own internal operations is highly concerning."