vSphere Storage - ESXi 5.1 - Documentation - VMware
vSphere Storage - ESXi 5.1 - Documentation - VMware
vSphere Storage - ESXi 5.1 - Documentation - VMware
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Using <strong>ESXi</strong> with iSCSI SAN 10<br />
You can use <strong>ESXi</strong> in conjunction with a storage area network (SAN), a specialized high-speed network that<br />
connects computer systems to high-performance storage subsystems. Using <strong>ESXi</strong> together with a SAN provides<br />
storage consolidation, improves reliability, and helps with disaster recovery.<br />
To use <strong>ESXi</strong> effectively with a SAN, you must have a working knowledge of <strong>ESXi</strong> systems and SAN concepts.<br />
Also, when you set up <strong>ESXi</strong> hosts to use Internet SCSI (iSCSI) SAN storage systems, you must be aware of<br />
certain special considerations that exist.<br />
This chapter includes the following topics:<br />
n “iSCSI SAN Concepts,” on page 71<br />
n “How Virtual Machines Access Data on an iSCSI SAN,” on page 76<br />
iSCSI SAN Concepts<br />
If you are an administrator who plans to set up <strong>ESXi</strong> hosts to work with iSCSI SANs, you must have a working<br />
knowledge of iSCSI concepts.<br />
iSCSI SANs use Ethernet connections between computer systems, or host servers, and high performance<br />
storage subsystems. The SAN components include iSCSI host bus adapters (HBAs) or Network Interface Cards<br />
(NICs) in the host servers, switches and routers that transport the storage traffic, cables, storage processors<br />
(SPs), and storage disk systems.<br />
iSCSI SAN uses a client-server architecture. The client, called iSCSI initiator, operates on your host. It initiates<br />
iSCSI sessions by issuing SCSI commands and transmitting them, encapsulated into iSCSI protocol, to a server.<br />
The server is known as an iSCSI target. The iSCSI target represents a physical storage system on the network.<br />
It can also be provided by a virtual iSCSI SAN, for example, an iSCSI target emulator running in a virtual<br />
machine. The iSCSI target responds to the initiator's commands by transmitting required iSCSI data.<br />
iSCSI Multipathing<br />
When transferring data between the host server and storage, the SAN uses a technique known as multipathing.<br />
Multipathing allows you to have more than one physical path from the <strong>ESXi</strong> host to a LUN on a storage system.<br />
Generally, a single path from a host to a LUN consists of an iSCSI adapter or NIC, switch ports, connecting<br />
cables, and the storage controller port. If any component of the path fails, the host selects another available<br />
path for I/O. The process of detecting a failed path and switching to another is called path failover.<br />
For more information on multipathing, see Chapter 20, “Understanding Multipathing and Failover,” on<br />
page 193.<br />
<strong>VMware</strong>, Inc. 71