Concept Guide

You can configure whether iSCSI frames are re-marked to contain the configured VLAN priority tag or IP DSCP when forwarded
through the switch.
NOTE: On a switch in which a large proportion of traffic is iSCSI, CoS queue assignments may interfere with other network
control-plane traffic, such as ARP or LACP. Balance preferential treatment of iSCSI traffic against the needs of other
critical data in the network.
Information Monitored in iSCSI Traffic Flows
iSCSI optimization examines the following data in packets and uses the data to track the session and create the classifier entries
that enable QoS treatment.
● Initiator’s IP Address
● Target’s IP Address
● ISID (Initiator defined session identifier)
● Initiator’s IQN (iSCSI qualified name)
● Target’s IQN
● Initiator’s TCP Port
● Target’s TCP Port
● Connection ID
● Aging
●
Up Time
If no iSCSI traffic is detected for a session during a user-configurable 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 EMC 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 flowing through an adjacent switch are not learned. Session monitoring
learns sessions that actually flow 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-Configuration 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 reconfigure the switch to enhance storage traffic flows.
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).
The following message displays the first time a Dell EqualLogic array is detected and describes the configuration changes that
are automatically performed:
%STKUNIT0-M:CP %IFMGR-5-IFM_ISCSI_AUTO_CONFIG: This switch is being configured for
optimal
conditions to support iSCSI traffic which will cause some automatic configuration to
occur
including jumbo frames and flow-control on all ports; no storm control and spanning-tree
port
fast to be enabled on the port of detection.
iSCSI Optimization
395