Server virtualization is all about maximizing the efficiency of physical resources. But it’s not just about optimal configuration; it’s also about the ability to respond to workloads in real-time, analysts say.
While virtualization products from VMware, Citrix and Oracle, in conjunction with tools from Richmond Hill, Ont.-based Cirba and Toronto-headquartered PlateSpin, can dynamically reallocate virtual machines across physical servers, the current iteration of Microsoft’s Virtual Server can’t, says Burton Group analyst Chris Wolfe, and that’s a drawback.
“In the large enterprise, it becomes a serious issue,” Wolfe says. “The future data centre is going to be able to balance your virtual workload across the exact number of physical servers that’s needed. So as my virtual workload goes down, I can simply power down physical servers that aren’t needed. As my virtual workload goes up, I can power on new physical servers and move the VMs to those resources as needed. So there could be some significant energy cost savings associated with that sort of mobility.”
Stephen Elliot, an analyst with IDC, says in the real world, supporting features like dynamic reallocation are must-haves. “Increasingly, if you’re talking to an enterprise, you’re talking about production,” he says, and features like motioning, physical to virtual migration, disaster recovery, file-level protection and configuration management are critical.
“In production, you need these features,” Elliott says. “In the lab, some of these features are starting off not as critical. In production, it’s gotta happen.”
Aside from the power savings, there are business advantages to dynamic reallocation, says Wolfe.
“If the sale of a new product is higher than expected and I get a very large increase in Web traffic, for example, I want my virtual infrastructure to be able to spin up servers on demand and allocate them to physical resources,” Wolfe says.
Bruce Cowper, senior program manager with Microsoft Canada, confirms that Virtual Server 2005 doesn’t support dynamic migration. Migration and management tools are handled by System Center Virtual Machine Manager, and migration requires the host machine to be offline momentarily.
“Normally, it takes seconds,” Cowper says. And dynamic migration is addressed by Microsoft’s recently announced Hyper-V hypervisor running on Virtual Server 2008, he says.
But Cirba’s co-founder and CTO, Andrew Hillier, wonders if that dynamism is necessary under all circumstances.
“I think this one is working itself out in the market right now,” Hillier says. “A lot of people when they use VMware assume there are going to be very fluid pools of resources flowing around. What we’re seeing is, as you go deeper into production environments and start to virtualize certain kinds of gear and all the back office stuff, there will be cases where motioning becomes a liability, where it creates excessive volatility.
“If you have workloads that are very sporadic in nature, time oriented, they might cause you to rebalance your pool around,” he says. “For workloads that are more consistent and constant, transaction processing type workloads, they tend to stack up quite nicely on servers with a very high level of utilization, almost a mainframe level of utilization. There may not be any reason to shift them around because there’s no transient nature to what there doing.”
Cirba’s Data Centre Intelligence software offers proactive placement. Historical analysis of utilization data allows administrators to set up the virtualization infrastructure in advance, according to the day’s predicted traffic.
“You can just set things up the way they should be, sharing resources, but not moving things around like crazy,” Hillier says. “And in other cases, things will move around a lot more. I think there will be a natural affinity for things to go one way or the other based on the types of servers that are being virtualized.”