About 165,000 web sites have been offline since Saturday because of a failed data center migration involving the web hosting company NaviSite Inc., based in Andover, Massachusetts. The problems have started on Saturday, when NaviSite tried to migrate and also replace hundreds of servers operated by Alabanza Corp., which was a web hosting company from Baltimore that NaviSite acquired in August.

According to Rathin Sinha, NaviSite’s spokesman, the company decided to physically move 200 of the 850 servers operated by Alabanza to its own data center from Andover, Massachusetts and then to virtually migrate the data from the rest of the older servers to new boxes. On Saturday, NaviSite informed its customers about the move and said that the web sites would be down for a while, as the migration was expected to be finished the very same day. But when NaviSite tried to transfer the data from the 650 servers that were still in Baltimore, it ran into several synchronization failures that kept multiplying; NaviSite realized that it could not meet the given deadline and because of this the company decided to physically move another 200 servers to Andover, so that the scope of the virtual migration could be reduced and the data transfer to be speeded up.

But it was not NaviSite’s lucky day! The hosts came up, but their URLs did not, which made the users to be able to access the web sites from their IP addresses, but not by using their URLs. Next, when the company was trying to solve this new problem, the network became overloaded because of all the users that were trying to get online. "What happened was first the URL could not match with the IP address and then IP did not match with the machine, so it took some time, and all this time we have a highly trafficked overloaded network.” – NaviSite’s spokesperson said adding that: "If there is one little problem, they multiply because there is a lot of dependencies."

Now although a big part of the web sites are now back online, the web hosting company’s spokesman could not say when everything would be back to normal and how much this problem would cost NaviSite.