The round-robin algorithm rotates path selection for a volume through all paths. For any  volume that uses the fixed-path policy, the first discovered preferred node path is chosen. The  VMW_PSP_MRU  policy selects the first working path, discovered at system boot time. If this path  becomes unavailable, the ESXi/ESX host switches to an alternative path and continues to use  the new path while it is available.  All these algorithms were modified with V4.0 and later to honor the IBM Spectrum Virtualize  preferred node that is discovered by using the  TPGS  command. Path failover is automatic in all  cases. If the round-robin algorithm is used, path failback might not return to a preferred node  path. Therefore, manually check pathing after any maintenance or problems occur. Update:  From vSphere version 5.5 and later, VMware multipath driver fully supports IBM  Spectrum Virtualize/Storwize V7000 ALUA preferred path algorithms. VMware  administrators should select Round Robin and validate that  VMW_SATP_ALUA is displayed .  This configuration reduces operational burden and improves cache hit rate by sending the  I/O to the preferred node. Our recommendation for NMP Round Robin configuration is to change the default value of  IOs before changing a path from the default 1,000 to 1. This will better spread the workload  among the paths, avoiding some high latency situations that are not visible at a SAN level. For  more information about how to change this setting, see the following  VMware KB : https://kb.vmware.com/s/article/2069356 The VMware multipathing software supports the following maximum configuration: Tip:  Each path to a volume equates to a single SCSI device. See the following VMware website for a complete list of maximums:  https://configmax.vmware.com/# 6.11.2 Multipathing configuration maximums GLYPH<SM590000> A total of 256 SCSI devices GLYPH<SM590000> Up to 32 paths to each volume GLYPH<SM590000> Up to 4096 paths per server Chapter 6. Hosts  305