vSphere Storage - ESXi 5.1 - Documentation - VMware

vSphere Storage
ESXi and SAN Use Cases
When used with a SAN, ESXi can benefit from multiple vSphere features, including Storage vMotion,
Distributed Resource Scheduler (DRS), High Availability, and so on.
Using ESXi in conjunction with a SAN is effective for the following tasks:
Storage consolidation
and simplification of
storage layout
Maintenance with zero
downtime
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. Choose a SAN for external storage to provide a simpler
system architecture along with other benefits.
When performing ESXi host or infrastructure maintenance, use vMotion to
migrate virtual machines to other host. If shared storage is on the SAN, you
can perform maintenance without interruptions to the users of the virtual
machines. Virtual machine working processes continue throughout a
migration.
Load balancing You can add a host to a DRS cluster, and the host's resources become part of
the cluster's resources. The distribution and usage of CPU and memory
resources for all hosts and virtual machines in the cluster are continuously
monitored. DRS compares these metrics to an ideal resource utilization. Ideal
utilization takes into account the attributes of the cluster's resource pools and
virtual machines, the current demand, and the imbalance target. It then
performs (or recommends) virtual machine migrations accordingly.
Disaster recovery You can use VMware High Availability to configure multiple ESXi hosts as a
cluster to provide rapid recovery from outages and cost-effective high
availability for applications running in virtual machines.
Simplified array
migrations and storage
upgrades
Specifics of Using SAN Storage with ESXi
When you purchase new storage systems or arrays, use Storage vMotion to
perform live automated migration of virtual machine disk files from existing
storage to their new destination without interruptions to the users of the virtual
machines.
Using a SAN in conjunction with an ESXi host differs from traditional SAN usage in a variety of ways.
When you use SAN storage with ESXi, keep in mind the following considerations:
n You cannot use SAN administration tools to directly access operating systems of virtual machines that
use the storage. With traditional tools, you can monitor only the VMware ESXi operating system. You use
the vSphere Client or the vSphere Web Client to monitor virtual machines.
n The HBA visible to the SAN administration tools is part of the ESXi system, not part of the virtual machine.
n Typically, your ESXi system performs multipathing for you.
28 VMware, Inc.