PowerCLI Script to set RDM LUNs to Perennially Reserved – Fixes Slow Boot of ESXi 5.1 with MSCS RDMs

vmware logoI’ve previously posted around this topic as part of another problem but having had to figure out the process again I think it’s worth re-posting a proper script for this. VMware KB 1016106 is snappily titled “ESXi/ESX hosts with visibility to RDM LUNs being used by MSCS nodes with RDMs may take a long time to boot or during LUN rescan” and describes the situation where booting ESXi (5.1 in my case) takes a huge amount of time to boot because it’s attempting to gain a SCSI reservation on an RDM disk used by MS Clustering Services. It also details the fix.

The process is fairly simple, but a bit labour intensive if you’re doing it manually on a large cluster.

  1. Retrieve the ScsiCanonicalName for each RDM
  2. Set the configuration for each RDM on each Host to “PerenniallyReserved”

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