iSCSI
is a protocol that supports access to remote, small computer system interface
(SCSI)-based storage devices over a TCP/IP network. iSCSI carries standard SCSI
commands over IP networks to facilitate data transfers over intranets, and to
manage storage over long distances. You can use iSCSI to transmit data over
local area networks (LANs), wide area networks (WANs), or even over the
Internet.
iSCSI relies on
standard Ethernet networking architecture. Specialized hardware such as host
bus adapters (HBA) or network switches are optional. iSCSI uses TCP/IP
(typically, TCP port 3260). This means that iSCSI simply enables two hosts to
negotiate tasks—for example, session establishment, flow control, and packet
size—and then exchange SCSI commands by using an existing Ethernet network. By
doing this, iSCSI uses a popular, high performance, local storage bus subsystem
architecture, and emulates it over LANs and WANs to create a storage area
networks (SANs). Unlike some SAN technologies, iSCSI requires no specialized
cabling. You can run it over the existing switching and IP infrastructure.
However, you can increase the performance of an iSCSI SAN deployment by
operating it on a dedicated network or subnet, as best practices recommend
An iSCSI SAN deployment includes
the following:
•
TCP/IP network. You can use standard network interface adapters and standard
Ethernet protocol network switches to connect the servers to the storage
device. To provide sufficient performance, the network should provide speeds of
at least 1 gigabit per second (Gbps), and should provide multiple paths to the
iSCSI target. As a best practice, use a dedicated physical and logical network
to achieve fast, reliable throughput.
•
iSCSI targets. This is another method of gaining access to storage. iSCSI
targets present, or advertise storage, similar to controllers for hard disk
drives of locally attached storage. However, this storage is accessed over a
network instead of locally. Many storage vendors implement hardware-level iSCSI
targets as part of their storage device’s hardware. Other devices or
appliances, such as Windows Storage Server 2012 devices, implement iSCSI
targets by using a software driver together with at least one Ethernet adapter.
Windows Server 2012 provides the iSCSI target server—which is effectively a
driver for the iSCSI protocol—as a role service.
•
iSCSI initiators. The iSCSI target displays storage to the iSCSI initiator
(also known as the client), which acts as a local disk controller for
the remote disks. All versions of Windows Server beginning with Windows Server® 2008 include the
iSCSI initiator, and can connect to iSCSI targets.
• iSCSI Qualified Name (IQN).
IQNs are globally unique identifiers that are used to address initiators and
targets on an iSCSI network. When you configure an iSCSI target, you must
configure the IQN for the iSCSI initiators that will be connecting to the target.
iSCSI initiators also use IQNs to connect to the iSCSI targets. However, if
name resolution on the iSCSI network is a possible issue, iSCSI endpoints (both
target and initiator) can be identified by their IP addresses.
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