Reference Guide

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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.
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 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 optimization allows you to reduce deployment time and management complexity in data centers.
In a data center network, Dell EqualLogic and Dell Compellent iSCSI storage arrays are connected to a
converged Ethernet network using the data center bridging exchange protocol (DCBx) through stacked
and/or nonstacked Ethernet switches.
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 Dell Compellent storage arrays where auto-detection is not
supported.
• Automatic configuration of switch ports after detection of storage arrays.
• 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.
• iSCSI DCBx TLVs are supported.
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 configured to use dot1p priority-queue
assignments to ensure that iSCSI traffic in these sessions receives priority treatment when forwarded on
stacked switch hardware.
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iSCSI Optimization