Virtual databases: An alternative solution

PolyServe's cluster file system provides much better storage utilisation.


Server virtualisation is an efficient way to save on server hardware costs, real estate, and management resources, but it isn’t the only way. Just ask the folks at Avanade, a systems integrator specialising in Microsoft solutions. For one government customer, Avanade had originally designed hundreds of SQL Servers in highly available MSCS (Microsoft Cluster Server) clusters, but the system was spiralling out of control.

“We had roughly 50 percent of the SQL Server nodes acting in a passive capacity,” says David K. Miller, Avanade’s director of technology and infrastructure in the U.K. “This was a potentially huge expenditure in server hardware, rack space, network and storage infrastructure. And we still had to monitor and patch them all.”

To reduce both its hardware and database software costs, Avanade turned to PolyServe Database Utility for SQL Server, which is based on the company’s Matrix Server virtualisation technology. As opposed to traditional server virtualisation, PolyServe uses a symmetrical cluster file system to allow all servers in a cluster to see all the data within the Windows file system, creating a single, virtualised storage and server pool. Previously, some instances of SQL Server might have used only 10 percent of their available storage, whereas others were bursting at the seams and would need to be taken offline to expand their storage. Sharing the storage pool improves overall storage utilisation, while still giving the performance benefits of dedicated servers.

PolyServe also gave Miller more hardware flexibility. “Unlike with MSCS, all the nodes in the cluster don’t have to be identical, so we had the option to mix two-way, four-way, and eight-way servers in the same cluster,” he says. “This would allow us to move an instance of a SQL Server from a two-node to an eight-node server for heavy overnight batch processing, while moving the off-peak online traffic from the eight-way to a four-way or two-way server at the same time, then moving them back the next morning.”

PolyServe’s “dynamic rehosting” feature can move SQL Server instances from server to server in seconds. It also allows every server in a cluster of as many as 16 nodes, active or passive, to act as a fail-over target for every other server. Compared with MSCS, which limits a cluster to eight nodes, Miller estimates that PolyServe’s approach has reduced the number of passive nodes by 80 percent across the enterprise.

“Server virtualisation was not the answer for us, as the processing requirements of our SQL Server deployments really required us to put them on their own physical platforms,” Miller says. “PolyServe’s product allowed us to reduce the number of physical servers by reducing the number of passive nodes.”

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