VMware Infrastructure 3 QLogic QDepth

By default, VMware Infrastructure 3 uses the QLogic QDepth default value of 32 to act as an execution throttle. As a best practice, QDepth should be limited to around eight to retain some headroom for expansion. Refer to VMware Knowledge Base article 1267 on how to adjust the QDepth for performance tuning. In general, the following formula applies to each path between the host machine and the array: [Total number of LUNs] * QDepth < [Array queue depth] Refer to VMware Knowledge Base article #1267 at www.vmware.com/support/kb/enduser/std_adp.php?p_faqid=1267 for more information on tuning QDepth. • The default queue depth value of 32 is satisfactory for Emulex HBA cards. • If you are using Microsoft® Windows® 2000 or Windows Server 2003 check your operating system timeout values. For a VMware environment, the DiskTimeOutValue must be set to 60 seconds. • Dynamic load balancing is currently not supported by VMware Infrastructure 3. However, for active/active arrays with fixed failover policy, load balancing can be achieved by manually assigning a LUN to a specific path. For more information, refer to the VMware document, “Server Configuration Guide,” at http://www.vmware.com/pdf/vi3_server_config.pdf.