Dell PowerVault ME4 Series Storage System Deployment Guide

If a controller module failure occurs, the affected controller module fails over to the partner controller module with little interruption to data flow. A failed controller module can be replaced without the need to shut down the storage system.

In a dual-controller module system, hosts use LUN-identifying information from both controller modules to determine the data paths are available to a volume. Assuming MPIO software is installed, a host can use any available data path to access a volume that is owned by either controller module. The path providing the best performance is through the host ports on the controller module that owns the volume . Both controller modules share one set of 1,024 LUNs (0-1,023) for use in mapping volumes to hosts.