Using ESXi with a SAN improves flexibility, efficiency, and reliability. Using ESXi with a SAN also supports centralized management, failover, and load balancing technologies.
The following are benefits of using ESXi with a SAN:
You can store data securely and configure multiple paths to your storage, eliminating a single point of failure.
Using a SAN with ESXi systems extends failure resistance to the server. When you use SAN storage, all applications can instantly be restarted on another host after the failure of the original host.
You can perform live migration of virtual machines using VMware vMotion.
Use VMware High Availability (HA) in conjunction with a SAN to restart virtual machines in their last known state on a different server if their host fails.
Use VMware Fault Tolerance (FT) to replicate protected virtual machines on two different hosts. Virtual machines continue to function without interruption on the secondary host if the primary one fails.
Use VMware Distributed Resource Scheduler (DRS) to migrate virtual machines from one host to another for load balancing. Because storage is on a shared SAN array, applications continue running seamlessly.
If you use VMware DRS clusters, put an ESXi host into maintenance mode to have the system migrate all running virtual machines to other ESXi hosts. You can then perform upgrades or other maintenance operations on the original host.
The portability and encapsulation of VMware virtual machines complements the shared nature of this storage. When virtual machines are located on SAN-based storage, you can quickly shut down a virtual machine on one server and power it up on another server, or suspend it on one server and resume operation on another server on the same network. This ability allows you to migrate computing resources while maintaining consistent shared access.