DELL PC7024 User Manual

iSCSI Optimization Commands

iSCSI Optimization provides a means of performing configuration specific to 

storage traffic and optionally giving traffic between iSCSI initiator and target 

systems special Quality of Service (QoS) treatment. 
iSCSI Optimization is best applied to mixed-traffic networks where iSCSI 

packets constitutes a portion of overall traffic. In these cases, the assignment 

of iSCSI packets to non-default CoS queues can provide flows with lower 

latency and avoid queue resource contention.
If iSCSI frames comprise most of the traffic passing through the switch, the 

system provides optimal throughput when all traffic is assigned to the default 

queue. An example of this situation is a Storage Area Network (SAN) where 

the switch is dedicated to interconnecting iSCSI Targets with Initiators. 

Using the default queue for this homogenous traffic provides the best 

performance in traffic burst handling and the most accurate 802.3x Flow 

Control Pause Frame generation. In these cases, the application of QoS 

treatment other than the default policy may result in less overall throughput 

or more packet loss.
By default, iSCSI optimization is enabled and iSCSI QoS treatment is 

disabled.
LLDP is used to detect the presence of EqualLogic storage arrays. When 

iSCSI optimization is enabled, and LLDP detects an EQL array on a port, 

that port configuration is changed to enable portfast and disable unicast 

storm control. Configuration changes appear in the running config and are 

not removed by disabling the feature or disconnecting the EQl array.
QoS treatment is accomplished by monitoring traffic to detect packets used 

by iSCSI stations to establish iSCSI sessions and connections. Data from 

these exchanges is used to create classification rules that assign the traffic 

between the stations to a configured traffic class. Packets in the flow are 

queued and scheduled for egress on the destination port based on these rules.

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