EMC's $635 million purchase of VMware left many people asking, VM who? But when you take a closer look at VMware you get: one, an interesting look at a server virtualization architecture that meshes with the emerging data center model; and two, a better idea of EMC's grand plan.

The 6-year-old company's claim to fame is a run-time layer called ESX that sits on Intel metal and makes it possible to support multiple operating system/application stacks on the same machine. "Basically we decouple software from hardware," says Edouard Bugnion, co-founder and chief architect.

ESX's benefits really shine when migrating from one OS to another, integrating computing environments or consolidating servers. Regarding the latter, ESX helps companies contend with the explosion of data center devices that has resulted from the habit of deploying one box for every service, even if each box is only running at 15% to 20% of capacity. VMware customers are putting in four- or eight-way Intel servers, loading ESX and migrating over existing OS/application stacks, some times realizing 20x consolidation, Bugnion says.

But where it gets interesting is when you combine ESX with VMware's management console, server provisioning tool and a new technology called VMotion that has been shipping for a quarter. VMotion lets you move live, stateful applications between environments or machines providing you have ESX on both, they share storage, and the source and destination are on the same subnet.

So in a blade server environment using VMware tools, if you detect a server loading problem you can slide in a new blade, configure the blade and migrate running OS/applications without taking down the original server.

That's possible because the OS/app stack are encapsulated and the CPU, memory, disk and NIC are all virtual. Moving a 4G-byte virtual machine over a 1G bit/sec link takes about a minute, Bugnion says. "We keep sockets alive and transactions from timing out by hiding latency."

The upshot is you can pool server resources, optimize workloads and eliminate the need to schedule hardware service windows - the nirvana scenario of the new data center. And it gets better: The next version of VMotion will be policy-based, meaning it all can be automated.