Administrator Guide

iSCSI Optimization
This chapter describes how to configure internet small computer system interface (iSCSI) optimization, which enables quality-of-service
(QoS) treatment for iSCSI traffic. The topics covered in this chapter include:
• iSCSI Optimization Overview
• Default iSCSI Optimization Values
• iSCSI Optimization Prerequisites
• Configuring iSCSI Optimization
• Displaying iSCSI Optimization Information
Topics:
• iSCSI Optimization Overview
• Default iSCSI Optimization Values
• iSCSI Optimization Prerequisites
• Configuring iSCSI Optimization
• Displaying iSCSI Optimization Information
iSCSI Optimization Overview
iSCSI is a TCP/IP-based protocol for establishing and managing connections between IP-based storage devices and initiators in a storage
area network (SAN).
iSCSI optimization enables the network switch to auto-detect Dell’s iSCSI storage arrays and triggers a self-configuration of several key
network configurations that enables optimization of the network for better storage traffic throughput. iSCSI is disabled by default.
iSCSI optimization also provides a means of monitoring iSCSI sessions and applying quality of service (QoS) policies on iSCSI traffic. When
enabled, iSCSI optimization allows a switch to monitor (snoop) the establishment and termination of iSCSI connections. The switch uses
the snooped information to detect iSCSI sessions and connections established through the switch.
iSCSI session monitoring over virtual link trunking (VLT) synchronizes the iSCSI session information between the VLT peers, allowing
session information to be available in both the VLT peers. You can enable or disable iSCSI when you configure VLT.
iSCSI optimization functions as follows:
• Auto-detection of EqualLogic storage arrays — the switch detects any active EqualLogic array directly attached to its ports.
• Manual configuration to detect Compellent storage arrays where auto-detection is not supported.
• Automatic configuration of switch ports after detection of storage arrays.
• If you configure flow-control, iSCSI uses the current configuration. If you do not configure flow-control, iSCSI auto-configures flow
control settings so that receive-only is enabled and transmit-only is disabled. .
• iSCSI monitoring sessions — the switch monitors and tracks active iSCSI sessions in connections on the switch, including port
information and iSCSI session information.
• iSCSI QoS — A user-configured iSCSI class of service (CoS) profile is applied to all iSCSI traffic. Classifier rules are used to direct the
iSCSI data traffic to queues that can be given preferential QoS treatment over other data passing through the switch. Preferential
treatment helps to avoid session interruptions during times of congestion that would otherwise cause dropped iSCSI packets.
NOTE:
After a switch is reloaded, powercycled, or upgraded, any information exchanged during the initial handshake is
not available. If the switch establishes communication after reloading, it detects that a session was in progress but
could not obtain complete information for it. Any incomplete information is not available in the show commands.
NOTE: After a switch is reloaded, powercycled, or upgraded, the system may display the ACL_AGENT-3-
ISCSI_OPT_MAX_SESS_LIMIT_REACHED: Monitored iSCSI sessions reached maximum limit log message.
This cannot be inferred as the maximum supported iSCSI sessions are reached. Also, number of iSCSI sessions
displayed on the system may show any number equal to or less than the maximum.
The following illustration shows iSCSI optimization between servers and a storage array in which a stack of three switches connect
installed servers (iSCSI initiators) to a storage array (iSCSI targets) in a SAN network. iSCSI optimization running on the master switch is
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