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To overcome the performance limitations of virtualized servers, Klein at the Saugus Union School District says, "We generally buy a high-performance machine, such as a blade server, with extremely fast IO for a virtualization host." Klein has virtualized five Hewlett-Packard (HP) Co. blade servers with the open-source Xen hypervisor and Citrix's XenServer.
"We only use Fibre Channel for shared storage, high-speed Serial Attached SCSI [SAS] drives and fast, multicore processors," says Klein. "Since you have multiple loads hitting the same IO channel and bus, it's important that each load be able to get on and off the channel as quickly as possible."
Several vendors have introduced tools and management appliances that alleviate the performance tax virtualized servers extract from the network. Onaro Inc.'s (soon to be acquired by Network Appliance Inc.) VM Insight lets server and storage admins view the dependencies between virtualized servers and their attached storage, and determine how changes to the FC or IP network and its server connections will affect overall performance. Gear6 and Xsigo Systems Inc. offer appliances that try to mitigate virtualized server performance bottlenecks. The Xsigo I/O Director and Gear6 Cachefx create virtual IO channels between servers and storage to reduce overhead and increase IO throughput.
VMs can be a boon to businesses because they consolidate
| operations, but they can also be a burden when IT considers the complexities of backing up, managing and tracking them. It will behoove storage administrators to learn the best ways to protect VMs in their environment and, with management and monitoring tools, control their growth.
This was first published in February 2008