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| virtual servers are forcing storage administrators to address data protection processes, such as replication, in new ways. And replication vendors are finding new avenues for their technology by leveraging VMware's VMotion technology.
VMotion, which has been around since the early days of VMware ESX Server, allows an administrator to migrate virtual servers from one physical host server to another.
"If you're going to move from Chicago to New York, it's going to take some time for those two systems to sync," says George Pradel, director of strategic alliances at Vizioncore, which makes tools to enhance the server virtualization platforms from VMware and other hypervisor vendors.
"VMotion syncs the memory between the two servers and then hands over control of that virtual machine to the receiving server," says Pradel, a one-time VMware systems engineer. "The advantage of VMotion is that the system is never out of production."
But VMotion has its limitations. For instance, "VMotion is great if your ESX host goes down, or if there's a hardware problem and you need to move virtual machines around," explains Bob Roudebush, director of solutions engineering at Double-Take Software, whose Double-Take for VMware Infrastructure tool replicates virtual machines. "But it doesn't save you from a fire, power outage, or a SAN or switch problem. VMotion is really intended for planned downtime," he says.
Compellent Technologies saw that limitation when it started working on the technology for its new Live Volume business continuity feature. Live Volume eliminates downtime for Compellent SAN users who need to migrate servers and storage for disaster recovery or onsite maintenance.
"Customers want to take advantage of VMotion when they move an application from one server to another," says Bob Fine, director of product marketing at Compellent. But sometimes they want to move an application not only from one server to another, but across a distance. According to Fine, Live Volume can detect when the access path changes between an application and the server and storage; it can also, if needed, automatically swap the data access from the primary to the secondary SAN.