Christopher explains it very well here:  [URL]
Hi,   I’ve inherited the following setup:   3x ESX 4.1U2 Host which are directly attached with 8GB FC to an EMC CX4-120. The Sp’s of the CX4-120 have Flare 4.30.0.5.509   In unisphere I found out that initiator type hasn’t been set and failover mode is set to 1. In vSphere I found that path selection had been set to MRU and storage Array Type to VMW_SATP_CX   Is it wise for me to configure the Cx4-120 to use ALUA, thus set failover mode to 4 and the initiator on Clarion Open?  And if so what would be the best setting for NMP? RR or Fixed?   Or is it best to put effort in using powerpath as NMP? I was told that powerpath is installed on the ESX hosts, but is there a way to verify it?    Thanks in advance for your help!
Best practice CX4-120 & ESX 4.1 initiator and failovermode