Ed Sperling

Ed Sperling, None

3/30/2009 @ 6:00AM

Painting The Data Center Green

We live in a physical world, but data lives in a virtual world. And now data is about to go even more virtual, tied less to a physical server and more to where resources can be be used effectively and efficiently.

Driven by runaway operating costs, pressure to become more environmentally friendly (and energy efficient) and the realities of multicore processors, virtualization solutions are being pitched by every major hardware vendor in the information technology world. Forbes caught up with Stephen Herrod, chief technology officer at VMware , to discuss the changes.

Forbes: Where is virtualization strongest?

Stephen Herrod: We work on the data center, the hosting/cloud world, and we have a very large effort around the desktop. On the data center side, the most generally misunderstood view of what we’re doing now comes from looking historically at what we were doing.

In the past, VMware was being used purely for server consolidation. It was a matter of taking underutilized servers and bringing them down to a smaller number of physical servers. We’ve been doing virtualization for 11 years, and eight years ago we had our first solution for server consolidation. From a top-of-mind standpoint, it was a capital savings approach. You would not need to buy a new data center. You would need fewer servers, fewer racks, fewer switch ports. That has been an easy sale because return on investment was very rapid.

Virtualization is an easy conceptual sale, but the reality is there are still all sorts of issues involving security, optimization and implementation.

Actually, there have been a lot more issues than that over time, and many of those were organizational, not just technical. For a data center manager, you may be used to a world where your server guy is here and your application guy is somewhere else, and they never talk. That’s no longer the case.

One of the most recent objections we encountered was from a networking team who felt they lost visibility into where the network packets were going. There are 50 virtual servers they can’t see into. One of our big initiatives has been to provide them with that visibility.

Is the reason for implementing virtualization changing?

So far, the No. 1 reason has been capital savings, and our big focus has been in understanding the operational expenses. After that, the advantage is that it becomes a strategic architecture that allows faster provisioning on behalf of your employees. The second big reason that people are moving to virtualization is that availability is better in a virtualized world.

We talk about availability in terms of planned downtime and unplanned downtime. Planned downtime is for maintenance, which may be done at 2 a.m. on Saturday. Now you can do a running virtual machine with zero downtime.

Are data center managers comfortable with shutting down portions of a data center?

This is distributed power management, and some people are nervous about that. People aren’t used to servers going off at random times. There’s work to make sure the management tools and processes are alerted. We also found that it’s better to throttle down servers than to physically turn one off and have another one running at full utilization. Optimizing that isn’t as intuitive as it sounded when I first began here.

Does it matter if you’re using a single-core or multicore machine to run virtualization?

Virtualization enables people to use multicore machines, and soon you won’t be able to buy less than four cores on a chip. We started originally on single-core systems with a resource scheduler and NUMA (non-uniform memory access) awareness. All machines have moved to that, but they are looking like scalar architectures.

We’re able to harness all the power from the cores. The number of cores has grown faster than the amount of physical memory or I/O bandwidth. Our task is to run as many virtual machines on a single server as possible with the service-level guarantees that data center managers have asked for.

Is there a limit?

From a management perspective, the more you run on a single server the better. From a resource standpoint, the big issue is availability. The more stuff running, the more that can go wrong. Some people will put in an artificial restraint. That’s risk management. There’s also an issue of balanced design. You want all your applications to run at the right performance level. If you have 100 cores but you only have 32 gigabytes of memory, you won’t be able to provide enough physical memory to each virtual machine.

Does a multithreaded application that can run in parallel run differently in a virtualized environment?

The same way it would run on a physical server, it will run on a virtual machine. If it’s multithreaded and able to exploit parallel physical systems, it will be able to take advantage of the same things in virtual systems.

How exactly does that work?

The virtual machine works the same as a physical machine. There will be between one and eight virtual processors. Those virtual processors look like real processors to the operating system and anything running above it. They have no idea they’re not on an HP server, for example.

We’re transparent to the application. That said, very few applications can take advantage of the multicore technology that’s available today. Databases are the only mainstream data center applications that scale well.

Can you add more resources for those applications with virtualization? So instead of just using 4 cores, you use 16 or 32 cores?

In theory, you could. We haven’t seen a need to do that yet. But the number of applications that can scale up is near zero. A financial application or rendering would run multiple instances, which could scale out across a number of servers. Even the highest-end database stops at 32-way.

How about for cloud computing? Is virtualization widely accepted there?

It depends on the cloud. With the ones focused on the enterprise like AT&T or British Telecom, security is their top concern. They care deeply about isolation. They call it multitenancy. That’s compared to small companies or spinoffs, which are more concerned about price.

One of the main attractions of virtualization is power savings. How much can it actually save a data center?

We spend a lot of time analyzing power usage. Taking a single server out of the data center is about the equivalent of planting 50 trees from the standpoint of carbon footprint or taking three cars off the road. What I’ve been seeing outside of the United States is government mandates that say by this date, your data center needs to be carbon neutral.

That’s somewhat ironic, considering most of the big data centers are in the United States.

Perhaps, but the data center is a very strong lever they can pull and virtualization is a big enabler for that. We have been working with the U.S. government on Energy Star ratings for servers and the amount of energy that can be saved through consolidation and powering down systems that aren’t needed.

See Also:

Taming The Data Beast

A.I. In The Enterprise

A New CIO Survival Strategy

Comments are turned off for this post.