HP-UX iSCSI Software Initiator Support Guide, HP-UX 11i v1 and 11i v2, July 2005

Chapter 2

HP-UX iSCSI Software Initiator Product Overview

Targets

The iSCSI Software Initiator is interoperable with all iSCSI Protocol Specification (RFC 3720) compliant

targets. No component of the iSCSI Software Initiator implementation is, in any way, HP proprietary.

The iSCSI Software Initiator supports the static discovery of targets and, optionally, the dynamic discovery of

targets.

Hardware Path Representation

The iSCSI virtual Host Bus Adapter (HBA) is defined in the IO tree with respect to a virtual root node, which

will always have a value of 255. The hardware path for iSCSI targets is built off of this virtual HBA node,

instead of being built off of a physical HBA node, as is currently done with Fibre Channel and parallel SCSI

targets. The interaction between the iSCSI session and a physical HBA is abstracted in the virtual HBA.

The external representation of the hardware path for an iSCSI LUN is:

255/<iscsi_virtual_HBA>/<session_instance>.<virtual_bus>.<virtual_target>.<lun>

where:

• iscsi_virtual_HBA represents a virtual HBA off of the virtual root node. The value of

iscsi_virtual_HBA is typically zero (0).

• session_instance is the iSCSI session instance number. The iSCSI session defines a SCSI I-T nexus for

transactions between the iSCSI initiator and the iSCSI target.

• virtual_bus is an instance number (ext_bus) of a SCSI-2 bus.

• virtual_target is a virtual representation of a SCSI-2 target.

• lun is the representation of a SCSI-2 logical unit number.

Because iSCSI targets define internal storage in SCSI-3 format, a mapping is required between the

SCSI-3 LUN and:

— The HP-UX SCSI-2 bus

— The HP-UX SCSI-2 target

— The HP-UX SCSI-2 LUN representation

The mapping used is equivalent to the mapping used by the HP-UX Fibre Channel driver.

The hardware path for iSCSI targets will be persistent across reboots. It is maintained in the /etc/ioconfig

file and used during system startup to reconstruct the IO tree.

Device Discovery

The implementation of iSCSI on HP-UX uses a static discovery algorithm as the default means of identifying

iSCSI targets (devices). As an option, dynamic discovery of targets is available using Service Location

Protocol (SLP).