vSphere Storage - ESXi 5.1 - Documentation - VMware

vSphere Storage
Ports in Fibre Channel SAN
In the context of this document, a port is the connection from a device into the SAN. Each node in the SAN,
such as a host, a storage device, or a fabric component has one or more ports that connect it to the SAN. Ports
are identified in a number of ways.
WWPN (World Wide Port
Name)
A globally unique identifier for a port that allows certain applications to access
the port. The FC switches discover the WWPN of a device or host and assign
a port address to the device.
Port_ID (or port address) Within a SAN, each port has a unique port ID that serves as the FC address for
the port. This unique ID enables routing of data through the SAN to that port.
The FC switches assign the port ID when the device logs in to the fabric. The
port ID is valid only while the device is logged on.
When N-Port ID Virtualization (NPIV) is used, a single FC HBA port (N-port) can register with the fabric by
using several WWPNs. This method allows an N-port to claim multiple fabric addresses, each of which appears
as a unique entity. When ESXi hosts use a SAN, these multiple, unique identifiers allow the assignment of
WWNs to individual virtual machines as part of their configuration.
Fibre Channel Storage Array Types
ESXi supports different storage systems and arrays.
The types of storage that your host supports include active-active, active-passive, and ALUA-compliant.
Active-active storage
system
Active-passive storage
system
Asymmetrical storage
system
Using Zoning with Fibre Channel SANs
Allows access to the LUNs simultaneously through all the storage ports that
are available without significant performance degradation. All the paths are
active at all times, unless a path fails.
A system in which one storage processor is actively providing access to a given
LUN. The other processors act as backup for the LUN and can be actively
providing access to other LUN I/O. I/O can be successfully sent only to an active
port for a given LUN. If access through the active storage port fails, one of the
passive storage processors can be activated by the servers accessing it.
Supports Asymmetric Logical Unit Access (ALUA). ALUA-complaint storage
systems provide different levels of access per port. ALUA allows hosts to
determine the states of target ports and prioritize paths. The host uses some of
the active paths as primary while others as secondary.
Zoning provides access control in the SAN topology. Zoning defines which HBAs can connect to which targets.
When you configure a SAN by using zoning, the devices outside a zone are not visible to the devices inside
the zone.
Zoning has the following effects:
n Reduces the number of targets and LUNs presented to a host.
n Controls and isolates paths in a fabric.
n Can prevent non-ESXi systems from accessing a particular storage system, and from possibly destroying
VMFS data.
n Can be used to separate different environments, for example, a test from a production environment.
36 VMware, Inc.