Computerworld - In an ideal world, disaster recovery strategies would include backup equipment ranging from a single server to an entire dark data center. In the real world, you can't afford to set up an entire extra data center that you hope you'll never use. At the same time, you can't ignore the need for real-time business continuity protection. Virtual machines that can concurrently host multiple operating systems may reduce your backup equipment and software costs by as much as 70%. The downside? Accepting a slight performance hit.
Virtual-machine-based server consolidation is a technology that's almost too good to be true. Its promised savings result from combining multiple servers and operating systems into one RAM-crammed, multiprocessor box.
The chief player in this market is Palo Alto, Calif.-based VMware Inc. Its virtual machine server software can run up to 20 operating systems concurrently—including all versions of Windows, from 3.1 to XP, and many flavors of Unix—in one physical box. VMware offers two virtual server products: GSX Server runs on Intel-based machines using Unix, Linux or Windows, while ESX Server contains its own base operating system.
Similar in purpose (but not structure) to an emulator, virtual machines create independent, isolated computing environments that include a BIOS, I/O systems (serial, parallel and Universal Serial Bus ports) and support for SCSI devices, as well as full network connectivity. For mixed environments, the software supports file sharing between Linux and Windows systems using Samba.
While the servers are virtual, the benefits are real: hardware savings as a result of server consolidation and reduced maintenance expenses. A reduction in your need for physical space may not yield a direct savings, but it can be an added advantage. Because virtual machines switch between operating systems in seconds and don't require a reboot, downtime in case of failure is measured in seconds. Also, if one system crashes, it won't affect any other virtual machines or the host server's operating system.
"As part of a disaster recovery plan, running independent multiple operating environments enables you to guarantee immediate data availability and integrity," says Jeremy Smith, president of Global Continuity PLC, a business continuity service provider and partner of VMware in England.
Liverpool, England-based beverage firm Halewood International Ltd. worked with Global Continuity to install two virtual servers using the Global Continuity/VMware technology. Halewood's objective was to reduce the cost of backup equipment and support and to locate backup equipment nearby for easy service and testing.
Before using Global Continuity's NeverFail backup software, Halewood's IT manager, Alec Stewart, backed up all of the company's data to a digital audiotape recorder and copied databases to another server each night. That made Halewood's data secure, but the company lacked real-time rollover capability in case of failure. Stewart says he also worried about data integrity and the system's ability to grow.
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