Driving to ConvergenceBy David Strom Print
As IT shops gain expertise in virtualized applications, they can also get a better handle on load balancing and availability—once the domain of clustering solutions.
Driving the Convergence
Several factors have come together to make this trend possible: First, the mainstream virtualization vendors—such as Citrix, Microsoft, Novell and VMware (see table below)—are getting more adept at migrating applications between virtual and physical servers. This makes it easier for IT managers to virtualize their applications and understand how they can be duplicated in the event of a communications outage or disaster.
Microsoft is helping things along by giving away its Hyper-V virtualization software as part of the Windows Server 2008 64-bit edition. With a few mouse clicks, you can turn a physical application into a virtual one. Novell’s PlateSpin and Cassatt’s Active Response both have migration tools that can move workloads from physical to virtual environments and vice versa with relative ease.
Also giving virtualization a boost is the fact that IT managers are doing a better job of understanding which of their applications can tolerate longer failovers, thus making them more suitable for virtualized solutions. “Eighty percent of data center applications don’t need to preserve their session state,” Oestreich says. “If you can tolerate a failover of one or two minutes on your less critical applications, then you can deploy virtualization.”
In those cases, virtualization is a way to deliver business continuity at a relatively low cost. But IT must understand the disaster timeframe that is acceptable when a failed resource needs to be restarted, and must know which applications are not transaction-based and can tolerate small gaps in continuous uptime.
“There are still times when you need clustering, such as when you can’t afford to lose a single transaction and have to restart this transaction on the new machine after a failover,” says Carl Drisko, an executive and data center evangelist at Novell. “If your virtual machine [VM] goes down, anything being processed in memory is going to be lost.”
In addition, there are specialty vendors that focus on providing better automation and high-availability orchestration solutions. “This software allows multiple systems to watch one another and restart on another system after a failure,” explains Dan Kusnetzky, a virtualization consultant based in Osprey, Fla. “In this case, it is possible to substitute the combination of virtual machine software and orchestration/automation software for clustering software.”
“The amount of time it takes to start an existing VM is a lot less than it takes to boot a physical server because you’re just taking the VM image and loading it into memory,” says Novell’s Drisko. “This can save minutes of precious time, especially when compared to the boot time of a heavily loaded Windows Server. We’ve been able to bring up a VM in milli-seconds with the right kinds of network-optimized storage interconnect fabric.”
Having this fast-restart feature has made it easier for enterprises to manage patches and server operating system updates, because they can readily bring up a new instance of their most current OS environment with a virtual machine.
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