System information

Overview of Using ESX/ESXi with a SAN
Using ESX/ESXi with a SAN improves flexibility, efficiency, and reliability. Using ESX/ESXi with a SAN also
supports centralized management and failover and load balancing technologies.
The following are benefits of using ESX/ESXi with a SAN:
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You can store data redundantly and configure multiple paths to your storage, eliminating a single point
of failure. ESX/ESXi systems provide multipathing by default for every virtual machine.
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Using a SAN with ESX/ESXi systems extends failure resistance to the server. When you use SAN storage,
all applications can instantly be restarted after host failure.
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You can perform live migration of virtual machines using VMware VMotion.
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Use VMware High Availability (HA) in conjunction with a SAN for a cold-standby solution that
guarantees an immediate, automatic response.
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Use VMware Distributed Resource Scheduler (DRS) to migrate virtual machines from one host to another
for load balancing. Because storage is on a SAN array, applications continue running seamlessly.
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If you use VMware DRS clusters, put an ESX/ESXi host into maintenance mode to have the system migrate
all running virtual machines to other ESX/ESXi hosts. You can then perform upgrades or other
maintenance operations.
The transportability 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.
ESX/ESXi and SAN Use Cases
You can perform a number of tasks when using ESX/ESXi with SAN.
Using ESX/ESXi in conjunction with SAN is effective for the following tasks:
Maintenance with zero
downtime
When performing an ESX/ESXi host or infrastructure maintenance, use
VMware DRS or VMotion to migrate virtual machines to other servers. If
shared storage is on the SAN, you can perform maintenance without
interruptions to the user.
Load balancing
Use VMotion or VMware DRS to migrate virtual machines to other hosts for
load balancing. If shared storage is on a SAN, you can perform load balancing
without interruption to the user.
Storage consolidation
and simplification of
storage layout
If you are working with multiple hosts, and each host is running multiple
virtual machines, the storage on the hosts is no longer sufficient and external
storage is required. Choosing a SAN for external storage results in a simpler
system architecture along with other benefits.
Start by reserving a large LUN and then allocate portions to virtual machines
as needed. LUN reservation and creation from the storage device needs to
happen only once.
Chapter 2 Using ESX/ESXi with Fibre Channel SAN
VMware, Inc. 17