Users Guide

You can congure whether the iSCSI optimization feature uses the VLAN priority or IP DSCP mapping to determine the trac class
queue. By default, iSCSI ows are assigned to dot1p priority 4. To map incoming iSCSI trac on an interface to a dot1p priority-queue
other than 4, use the CoS dot1p-priority command (refer to QoS dot1p Trac Classication and Queue Assignment). Dell
Networking recommends setting the CoS dot1p priority-queue to 0 (zero).
You can congure whether iSCSI frames are re-marked to contain the congured VLAN priority tag or IP DSCP when forwarded
through the switch.
NOTE: On a switch in which a large proportion of trac is iSCSI, CoS queue assignments may interfere with other
network control-plane trac, such as ARP or LACP. Balance preferential treatment of iSCSI trac against the needs of
other critical data in the network.
Information Monitored in iSCSI Trac Flows
iSCSI optimization examines the following data in packets and uses the data to track the session and create the classier entries that
enable QoS treatment.
• Initiator’s IP Address
• Target’s IP Address
• ISID (Initiator dened session identier)
• Initiator’s IQN (iSCSI qualied name)
• Target’s IQN
• Initiator’s TCP Port
• Target’s TCP Port
• Connection ID
• Aging
• Up Time
If no iSCSI trac is detected for a session during a user-congurable aging period, the session data is cleared.
If more than 256 simultaneous sessions are logged continuously, the following message displays indicating the queue rate limit has
been reached:
%STKUNIT2-M:CP %iSCSI-5-ISCSI_OPT_MAX_SESS_EXCEEDED: New iSCSI Session Ignored: ISID -
400001370000 InitiatorName - iqn.1991-05.com.microsoft:dt-brcd-cna-2 TargetName -
iqn.2001-05.com.equallogic:4-52aed6-b90d9446c-162466364804fa49-wj-v1 TSIH - 0"
NOTE: If you are using EqualLogic or Compellent storage arrays, more than 256 simultaneous iSCSI sessions are
possible. However, iSCSI session monitoring is not capable of monitoring more than 256 simultaneous iSCSI sessions. If
this number is exceeded, sessions may display as unknown in session monitoring output. Dell Networking recommends
that you disable iSCSI session monitoring for EqualLogic and Compellent storage arrays or for installations with more
than 256 simultaneous iSCSI sessions.
Only sessions the switch observes are learned; sessions owing through an adjacent switch are not learned. Session monitoring
learns sessions that actually ow through the switch, it does not learn all sessions in the entire topology.
After a switch is reloaded, any information exchanged during the initial handshake is not available. If the switch picks up the
communication after reloading, it would detect a session was in progress but could not obtain complete information for it. Any
incomplete information of this type would not be available in the show commands.
Detection and Auto-Conguration for Dell EqualLogic Arrays
The iSCSI optimization feature includes auto-provisioning support with the ability to detect directly connected Dell EqualLogic
storage arrays and automatically recongure the switch to enhance storage trac ows.
The switch uses the link layer discovery protocol (LLDP) to discover Dell EqualLogic devices on the network. LLDP is enabled by
default. For more information about LLDP, refer to Link Layer Discovery Protocol (LLDP).
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iSCSI Optimization