Home > Storage > PowerVault > Guides > Dell PowerVault ME5 Series: VMware vSphere Best Practices > Asymmetric Logical Unit Access
PowerVault ME5 storage uses Unified LUN Presentation (ULP), which can expose all LUNs through all host ports on both controllers. The storage system appears as an active/active system to the host. The host can choose any available path to access a LUN regardless of disk group ownership. When ULP is in use, the controller operating or redundancy mode is shown as active/active ULP. ULP uses the Asymmetric Logical Unit Access (ALUA) extensions to negotiate paths with the ALUA-aware operating systems. If the hosts are not ALUA-aware, all paths are treated as equal even though some paths might have better latency than others.
vSphere ESXi is an ALUA-aware operating system, and no extra configuration is required. Each datastore has two, four, or eight active paths depending upon the controller configuration (SAS, combined FC/iSCSI controller, or dedicated FC/iSCSI). Half of the paths identified as active are optimized, and the other half are identified as active non-optimized.