Scalable Storage Performance

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August 11, 2008

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VMware ESX enables multiple hosts to share the same physical storage reliably through its highly optimized storage stack and VMware Virtual Machine File System (VMFS). To gain the greatest advantage from shared storage, it is important to understand the potential bottlenecks at various layers and make the necessary configuration changes to get optimal storage performance.This paper presents the results of our studies on storage scalability in a virtual environment with many ESX hosts, many LUNs, or many of both. It examines the effects of I/O queuing at various layers in a virtual infrastructure as more and more virtual machines share the same storage. It considers the effects of SCSI reservations on virtual machine I/O performance. And it looks at ways to mitigate bandwidth bottlenecks when multiple LUNs are connected to a single ESX host. It provides recommendations you can follow to avoid overcommitting storage resources.