HP StorageWorks Fabric OS 6.x administrator guide (5697-7344, March 2008)

Fabric OS 6.x administrator guide 343
QoS on E_Ports
In addition to configuring the hosts and targets in a zone, you must also enable QoS on individual E_Ports
that might carry traffic between the given host and target pairs. Path selection between the “host,target”
pairs is governed by FSPF rules and is not affected by QoS priorities. By default, QoS is enabled on
E_Ports in port configuration. For example, in Figure 26, QoS should be enabled on the encircled E_Ports.
Figure 26 QoS with E_Ports enabled
You need to enable QoS on the E_Ports on both ISLs between Domain 3 and Domain 4 because either
path might be selected to carry the traffic.
You do not need to enable QoS on the E_Ports on the ISLs between Domain 1 and Domain 2 and between
Domain 2 and Domain 3, because these are not the shortest paths between the hosts and the targets.
However, if the ISL between Domain 1 and Domain 3 is broken, then the path through Domain 2 would be
used.
To guarantee traffic priority, you should enable QoS on all possible E_Ports. Alternatively, you could use a
TI zone to limit the E_Ports that carry the traffic between a “host,target” pair and enable QoS on only those
E_Ports.
If QoS is not enabled on an E_Port, the traffic prioritization stops at that point. For example, in Figure 26 if
you disabled QoS on E_Ports “3,12” and “3,13” then the traffic from H1 and H2 to S3 would be low
priority from the hosts to Domain 3, but would switch to the default (medium) priority from Domain 3 to the
target S3.
Supported configurations for traffic prioritization
Note the following configuration rules for traffic prioritization:
IMPORTANT: All switches in the fabric must be running Fabric OS 6.0.0 or higher. If QoS traffic crosses
an ISL for a switch running an earlier firmware version, the frames are dropped.
• By default, all devices are assigned medium priority. To be assigned high or low priority, hosts and
targets must be connected to a DC Director. To preserve the priority level across ISLs, the switches must
be running Fabric OS 6.0.0 or later and must be one of the following: HP StorageWorks SAN Switch
4/32, 4/64 SAN Switch, SAN Switch 4/32B, 400 Multi-protocol Router, 4/256 SAN Director, or DC
Director.
• If a host and target are included in two or more QoS zones with different priorities, the zone with the
lowest priority takes precedence. For example, if an effective zone configuration has QOSH_z1 (H,T)
and QOSL_z2 (H,T), the traffic flow between H and T will be of low QoS priority.
Additionally, if QOSH_z1 (H,T) overlaps with a “domain,port” zone at the H port, the traffic flow
between H and T is dropped to medium priority and the H port is marked as a session-based soft
zoning port.
• Traffic prioritization is not supported on 10 Gbps ISLs.
7
12
3
14
15
16
8
13
Domain 1 Domain 3
Domain 4
Domain 2
H1
19
S3
S2
S1
H2
= High priority
= Medium priority
= Low priority
= E_Ports with
QoS enabled