Iscsi Details - IBM TotalStorage DS300 Best Practices Manual

Application Server
Client Desktop
Figure 2-1 iSCSI components
iSCSI Initiator: This consists of either software drivers or hardware adapters
that initiate the SCSI request over IP to a target server. iSCSI initiators are
available in software or hardware varieties. These drivers coexist with existing
SCSI devices without disruption.
iSCSI Target: This software manages the SCSI over IP requests on the
target device.
iSCSI device discovery: iSCSI device discovery software sits outside the
datastream providing TCP/IP fabric services to aid device discovery, storage
policy, logical unit number (LUN) virtualization (partitioning, mapping, volume
management). See "iSCSI discovery" on page 14 for more information.
All iSCSI sessions are started by a client (application server or client desktop)
requesting access to a target device.

2.2.1 iSCSI details

Internet SCSI (iSCSI) is defined in IETF RFC 3720. It allows SCSI block I/O
protocols (commands, sequences and attributes) to be sent over a network using
the TCP/IP protocol. This is similar to the way SCSI commands are already
mapped to Fibre Channel, parallel SCSI, and SSA media. Do not confuse this
with the SCSI cabling transport mechanism. We are talking about protocols.
We have discussed in general terms what iSCSI is supposed to be and its
components. In an later section, we will compare it to Network Attached Storage
Initiator
SCSI (Block I/O) Protocol
IP
Initiator
iSCSI device
discovery
Target
Chapter 2. iSCSI overview
13