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13
Mass Storage over IP Networks:
1 3
iSCSI
One of the central tasks in computer centers and when operating servers is providing hard disk
capacity for server systems. Fibre Channel is often used for this purpose. iSCSI (Internet SCSI)
solutions provide a lower-cost alternative to Fibre Channel that can leverage commodity servers and
Ethernet networking equipment. Linux iSCSI provides iSCSI initiator and target software for
connecting Linux servers to central storage systems.
iSCSI SAN with an iSNS Server
Figure 13-1
iSCSI is a storage networking protocol that facilitates data transfers of SCSI packets over TCP/IP
networks between block storage devices and servers. iSCSI target software runs on the target server
and defines the logical units as iSCSI target devices. iSCSI initiator software runs on different
servers and connects to the target devices to make the storage devices available on that server.
IMPORTANT: It is not supported to run iSCSI target software and iSCSI initiator software on the
same server in a production environment.
The iSCSI target and initiator servers communicate by sending SCSI packets at the IP level in your
LAN. When an application running on the initiator server starts an inquiry for an iSCSI target
device, the operating system produces the necessary SCSI commands. The SCSI commands are then
embedded in IP packets and encrypted as necessary by software that is commonly known as the
iSCSI initiator. The packets are transferred across the internal IP network to the corresponding
iSCSI remote station, called the iSCSI target.
Mass Storage over IP Networks: iSCSI
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