Iscsi Multisession Configuration And Support - IBM V7000 Introduction And Implementation Manual

Figure 11-4 compares the features of iSCSI adapter options.
Definition Definition
Offloaded burden Offloaded burden
Burden managed by Burden managed by
server CPU server CPU
Require software- Require software-
based initiator based initiator
iSCSI performance iSCSI performance
Cost Cost
Figure 11-4 Comparison of iSCSI adapter technologies

11.3.3 iSCSI multisession configuration and support

Multisession support, or host-level multipath support, provides multiple paths between iSCSI
initiators and targets, which are used for high availability and load balancing.
Some products require that an iSCSI initiator log in with a specific IP address of the target
versus logging in with a target name. Logging in with a target name in those products causes
the iSCSI initiator to log into all of the IP addresses in the target and causes session
reinstantiation that results in session loss of the previous log in. Flex System V7000 Storage
Node offers single subnet multisession configurations and multiple and dual subnet
multisession configurations that remove the restriction against logging into a target name.
iSCSI initiators use Internet storage name service (iSNS) servers to log in, which enables the
discovery of the iSCSI targets and their IP addresses.
An iSCSI session is a TCP relationship between an iSCSI initiator node port and an iSCSI
target node port. After being established, iSCSI control, data, and status messages are
communicated over the session.
Each session is identified with multiple iSCSI initiator names and the target name plus the
iSCSI initiator session ID (ISID) plus the target portal group tag (target-side ID).
The Flex System V7000 Storage Node multisession approach is to have relationships
between multiple initiator instances (separate ISIDs) to a single target portal group in an
iSCSI target. Such an approach is similar to having multiple SCSI initiator ports from the
same iSCSI initiator device have relationships with a single SCSI target port.
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IBM Flex System V7000 Storage Node Introduction and Implementation Guide
NIC NIC
A specialized NIC that A specialized NIC that
Provides Ethernet Provides Ethernet
provides additional provides additional
connectivity connectivity
functionality functionality
Physical and data link Physical and data link TCP/IP, physical and TCP/IP, physical and
communication communication data link communication data link communication
iSCSI protocol iSCSI protocol
iSCSI protocol iSCSI protocol
management and TCP/IP management and TCP/IP
management management
protocol management protocol management
Yes Yes
Adequate Adequate
$ $
TOE TOE iSCSI HBA iSCSI HBA
An HBA that provides An HBA that provides
Ethernet connectivity and Ethernet connectivity and
additional functionality additional functionality
iSCSI read/write iSCSI read/write
processing, TCP/IP processing, TCP/IP
processing, physical and processing, physical and
data link communication data link communication
None None
Yes Yes
Good Good Best Best
$$ $$ $$$$ $$$$
No No