Another Tough Day at Rackspace

Rackspace Hosting's Dallas data center experienced another power outage Tuesday. The downtime was shorter and appears to have affected fewer customers than last week's outage at the same facility, but gained media coverage in TechCrunch and the investing blogs Tech Trader Daily and Silicon Alley Insider.

Tuesday's incident was caused by a failed bus duct in the data center's power infrastructure, which affected customers on one UPS cluster. Rackspace was able to bypass the UPS and restore power using its backup generators. The power problems also caused some network problems. As of 8 p.m. Central time, the affected cluster was still being supported by generator power.

"We are still in the process of determining why the bus duct failed and why customers experienced downtime as a result of this issue," Rackspace reported in an update on its blog. "Customers supported by UPS cluster A are currently being powered by generators, which are running reliably and predictably. The bus duct replacement is underway and, when complete, will allow us to switch back to utility power."

Rackspace expects to issue customer service credits from the June 29 data center outage of between $2.5 million and $3.5 million, the company said in an SEC filing. An unusual series of equipment failures contributed to the outage, in which several parts of the Dallas facility lost power.