Dell Networking 7048, Справочное руководство

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iSCSI Optimization Commands
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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.
In addition, if configured, the packets can be updated with IEEE 802.1p or
IP-DSCP values. This is done by enabling remark . Remarking packets with
priority data provides special QoS treatment as the packets continue through
the network.
2CSPC4.X7000-SWUM204.book Page 569 Friday, March 15, 2013 8:22 AM