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Block storage (both iSCSI and FC) presented to vSphere hosts from Dell Technologies Unity has the native Path Selection Policy (PSP) of round robin (RR) applied by default. While RR is the recommended PSP to apply to Dell Technologies Unity block storage, the default number of I/Os between switching paths is 1000. By reducing this value, all paths are more efficiently utilized. Additional information on this topic can be found in the Adjusting Round Robin IOPS limit from default 1000 to 1 article in the VMware Knowledge Base.
Internal lab testing has indicated that adjusting the RR policy to iops=1 has shown up to a 121% increase in IOPS, and up to a 32% reduction in latency for vVol and VMFS datastores. It is recommended to test this in your environment to determine if this change positively effects your workloads.
A claim rule can be created to automatically set this value on future LUNs mapped to the host. This must be performed on all hosts and requires a reboot to take effect.
esxcli storage nmp satp rule add --satp "VMW_SATP_ALUA_CX" --vendor "DGC" --psp "VMW_PSP_RR" --psp-option "iops=1" --claim-option="tpgs_on"