Some data centers also have floor-level and rack-level isolators. In addition, all server racks, cooling equipment and other gear is secured firmly to the floor. "I see some U.S. data centers with racks just sitting on the floor, and you don't see that in Japan," he said.

The shock absorbers are most effective at the building level, Yamanaka said, and some of those at the rack-level did not work during the earthquake. Nevertheless, he said, only five server racks were reported critically damaged in all of Japan's data centers.

Another mitigating factor was that 70 percent of Japan's data centers are in the Tokyo region, which escaped relatively lightly. There are no data centers in the northeast where the tsunami hit, in part because that's precisely where tsunamis are expected. Nevertheless, the ground shook quite violently in Tokyo, rocking up to 10 centimeters to the right and left for almost two minutes.

Some companies have altered construction plans and are moving data center projects to the west of the country, which is considered safest, Yamanaka said.

Disaster recovery plans generally went smoothly. Where power was cut off, uninterruptible power supplies and diesel-powered generators kicked in, and companies were quick to order more fuel, Yamanaka said.