On storage controllers in combination vSphere 5.x multi path IO, path selecting policy should be Round Robin (always check if your storage supports this). When receiving the LUN it happens that those PSP are defaulted to Fixed. You can change the PSP policies of all attached storage with this PowerCLI oneliner (Round Robin in the example):

get-cluster -Name “Cluster” | Get-VMHost | Get-ScsiLun -LunType disk | Where-Object {$_.MultipathPolicy -ne “RoundRobin”} | Set-ScsiLun -MultipathPolicy “RoundRobin”

A little caution when you have storage from mixed storage providers (mixed storage controllers without a SVC,Vplex or such layer).

What does this one do:

– get-cluster -Name ”Cluster”; Retreives the cluster information for Cluster. This command can be replaced with get-datacenter. And pipe’s this information to:

– Get-VMHost; retreives the hosts information (one by one in from the cluster). The output is piped to:

– Get-ScsiLun – Luntype disk | Where-Object {$_.MultipathPolicy -ne “RoundRobin}

Get de Scsi Lun of type disk en checks if this object current policy is not equal with Rond Robin. The output is piped to:

– Set-ScsiLun -MultipathPolicy “RoundRobin. The Lun found with previous part is changed to a RoundRobin policy.

The policies can be set to:

RoundRobin, MostRecentlyUsed, Fixed or Unknown.

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