Service Manual

• iSCSI QoS — A user-configured iSCSI class of service (CoS) profile is applied to all iSCSI traffic. Classifier rules are used to
direct the iSCSI data traffic 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 configured to use dot1p priority-queue assignments to ensure that iSCSI traffic in these sessions receives
priority treatment when forwarded on stacked switch hardware.
Figure 61. iSCSI Optimization Example
Monitoring iSCSI Traffic Flows
The switch snoops iSCSI session-establishment and termination packets by installing classifier rules that trap iSCSI protocol
packets to the CPU for examination.
Devices that initiate iSCSI sessions usually use well-known TCP ports 3260 or 860 to contact targets. When you enable iSCSI
optimization, by default the switch identifies IP packets to or from these ports as iSCSI traffic.
You can configure the switch to monitor traffic for additional port numbers or a combination of port number and target IP
address, and you can remove the well-known port numbers from monitoring.
iSCSI Optimization 457