How it works...

A path to a LUN includes the HBA or initiator, the fabric/network switches, and the storage controllers in the array. The availability of a path will be affected if any of these hardware components along the path fail or stop functioning. Multipathing is a method for configuring and maintaining multiple paths between the host and the storage array. Although redundant fabric switches will be used to achieve this, the multipathing information available at ESXi will not show the switches that are involved.

Storage multipathing on an ESXi host is achieved with the help of a framework of APIs called Pluggable Storage Architecture (PSA). The APIs can be used by the storage vendors to develop Multipathing Plugins (MPPs), thus enabling a closer integration of their storage devices. Some examples of available third-party MPPs are as follows:

EMC PowerPath
Dell EqualLogic MEM for iSCSI multipathing
VERITAS dynamic multipathing for VMware

The default multipathing plugin on an ESXi host is called a Native Multipathing Plugin (NMP). The NMP adds support for all the supported storage arrays in the VMware compatibility list.

The following sections will help you to understand how the NMP works and the different storage types supported in a vSphere environment.

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Table of Contents for
How it works...