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Table Of Contents
The client, called iSCSI initiator, operates on your ESXi host. It initiates iSCSI sessions by issuing SCSI
commands and transmitting them, encapsulated into the iSCSI protocol, to an iSCSI server. The server is
known as an iSCSI target. Typically, the iSCSI target represents a physical storage system on the
network.
The target can also be 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 transmitting required iSCSI data.
iSCSI Multipathing
When transferring data between the host server and storage, the SAN uses a technique known as
multipathing. With multipathing, your ESXi host can have more than one physical path 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 18 Understanding Multipathing and Failover.
Nodes and Ports in the iSCSI SAN
A single discoverable entity on the iSCSI SAN, such as an initiator or a target, represents an iSCSI node.
Each node has a node name. ESXi uses several methods to identify a node.
IP Address Each iSCSI node can have an IP address associated with it so that routing
and switching equipment on your network can establish the connection
between the host and storage. This address is like the IP address that you
assign to your computer to get access to your company's network or the
Internet.
iSCSI Name A worldwide unique name for identifying the node. iSCSI uses the iSCSI
Qualified Name (IQN) and Extended Unique Identifier (EUI).
By default, ESXi generates unique iSCSI names for your iSCSI initiators,
for example, iqn.1998-01.com.vmware:iscsitestox-68158ef2.
Usually, you do not have to change the default value, but if you do, make
sure that the new iSCSI name you enter is worldwide unique.
iSCSI Alias A more manageable name for an iSCSI device or port used instead of the
iSCSI name. iSCSI aliases are not unique and are intended to be a friendly
name to associate with a port.
Each node has one or more ports that connect it to the SAN. iSCSI ports are end-points of an iSCSI
session.
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