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iSCSI Optimization

This chapter describes how to congure internet small computer system interface (iSCSI) optimization, which enables quality-of-service

(QoS) treatment for iSCSI trac.

Topics:

• iSCSI Optimization Overview

• Default iSCSI Optimization Values

• iSCSI Optimization Prerequisites

• Conguring 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 provides a means of monitoring iSCSI sessions and applying quality of service (QoS) policies on iSCSI trac. 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 conguration to detect Dell Compellent storage arrays where auto-detection is not supported.

• Automatic conguration 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-congured iSCSI class of service (CoS) prole is applied to all iSCSI trac. Classier rules are used to direct the

iSCSI data trac 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 congured

to use dot1p priority-queue assignments to ensure that iSCSI trac in these sessions receives priority treatment when forwarded on

stacked switch hardware.

iSCSI Optimization 473