vSphere Storage - ESXi 5.1 - Documentation - VMware

Using ESXi with Fibre Channel SAN 3
When you set up ESXi hosts to use FC SAN storage arrays, special considerations are necessary. This section
provides introductory information about how to use ESXi with a FC SAN array.
This chapter includes the following topics:
n “Fibre Channel SAN Concepts,” on page 35
n “Using Zoning with Fibre Channel SANs,” on page 36
n “How Virtual Machines Access Data on a Fibre Channel SAN,” on page 37
Fibre Channel SAN Concepts
If you are an ESXi administrator planning to set up hosts to work with SANs, you must have a working
knowledge of SAN concepts. You can find information about SANs in print and on the Internet. Because this
industry changes constantly, check these resources frequently.
If you are new to SAN technology, familiarize yourself with the basic terminology.
A storage area network (SAN) is a specialized high-speed network that connects computer systems, or host
servers, to high performance storage subsystems. The SAN components include host bus adapters (HBAs) in
the host servers, switches that help route storage traffic, cables, storage processors (SPs), and storage disk
arrays.
A SAN topology with at least one switch present on the network forms a SAN fabric.
To transfer traffic from host servers to shared storage, the SAN uses the Fibre Channel (FC) protocol that
packages SCSI commands into Fibre Channel frames.
To restrict server access to storage arrays not allocated to that server, the SAN uses zoning. Typically, zones
are created for each group of servers that access a shared group of storage devices and LUNs. Zones define
which HBAs can connect to which SPs. Devices outside a zone are not visible to the devices inside the zone.
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.
When transferring data between the host server and storage, the SAN uses a technique known as multipathing.
Multipathing allows you to have more than one physical path from the ESXi host to a LUN on a storage system.
Generally, a single path from a host to a LUN consists of an HBA, switch ports, connecting cables, and the
storage controller port. If any component of the path fails, the host selects another available path for I/O. The
process of detecting a failed path and switching to another is called path failover.
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