System information

Zoning is similar to LUN masking, which is commonly used for permission management. LUN masking is a
process that makes a LUN available to some hosts and unavailable to other hosts. Usually, LUN masking is
performed at the SP or server level.
Ports
In the context of this document, a port is the connection from a device into the SAN. Each node in the SAN, a
host, storage device, and 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)
In the 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 ESX/ESXi hosts use a SAN, these multiple, unique identifiers allow the assignment
of WWNs to individual virtual machines as part of their configuration.
Multipathing and Path Failover
When transferring data between the host server and storage, the SAN uses a multipathing technique.
Multipathing allows you to have more than one physical path from the ESX/ESXi host to a LUN on a storage
system.
If a path or any component along the path, HBA or NIC, cable, switch or switch port, or storage processor,
fails, the server selects another of the available paths. The process of detecting a failed path and switching to
another is called path failover.
Storage System Types
Storage disk systems can be active-active and active-passive.
ESX/ESXi supports the following types of storage systems:
n
An active-active storage system, which 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.
n
An active-passive storage system, in which one port is actively providing access to a given LUN. The other
ports 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 primary storage port fails,
one of the secondary ports or storage processors becomes active, either automatically or through
administrator intervention.
Fibre Channel SAN Configuration Guide
16 VMware, Inc.