SIMS 3.5 is a high-performance, highly scalable mail delivery and access system. Since mail is critical to enterprises and ISP customers, many SIMS customers wish to run SIMS on a cluster to get higher availability via fail-over to a surviving member of the cluster.For this reason, SIMS 3.5 provides Asymmetric High Availability (HA) configurations. In this configuration, all the SIMS binaries, configuration files, message queues, and message store reside on a shared disk. When a switch-over occurs, the disk is unmounted from the failing system and mounted on the surviving system.