6.0.1

Table Of Contents
Using ESXi with iSCSI SAN 9
You can use ESXi in conjunction with a storage area network (SAN), a specialized high-speed network that
connects computer systems to high-performance storage subsystems. Using ESXi together with a SAN
provides storage consolidation, improves reliability, and helps with disaster recovery.
To use ESXi eectively with a SAN, you must have a working knowledge of ESXi systems and SAN
concepts. Also, when you set up ESXi hosts to use Internet SCSI (iSCSI) SAN storage systems, you must be
aware of certain special considerations that exist.
This chapter includes the following topics:
n
“iSCSI SAN Concepts,” on page 63
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“How Virtual Machines Access Data on an iSCSI SAN,” on page 68
iSCSI SAN Concepts
If you are an administrator who plans to set up ESXi hosts to work with iSCSI SANs, you must have a
working knowledge of iSCSI concepts.
iSCSI SANs use Ethernet connections between computer systems, or host servers, and high performance
storage subsystems. The SAN components include iSCSI host bus adapters (HBAs) or Network Interface
Cards (NICs) in the host servers, switches and routers that transport the storage trac, cables, storage
processors (SPs), and storage disk systems.
iSCSI SAN uses a client-server architecture. The client, called iSCSI initiator, operates on your host. It
initiates iSCSI sessions by issuing SCSI commands and transmiing them, encapsulated into iSCSI protocol,
to a server. The server is known as an iSCSI target. The iSCSI target represents a physical storage system on
the network. It can also be provided by a virtual iSCSI SAN, for example, an iSCSI target emulator running
in a virtual machine. The iSCSI target responds to the initiator's commands by transmiing required iSCSI
data.
iSCSI Multipathing
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 iSCSI adapter or NIC, 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.
For more information on multipathing, see Chapter 17, “Understanding Multipathing and Failover,” on
page 183.
VMware, Inc.
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