Using Dynamic Load Sharing - HP AE370A - Brocade 4Gb SAN Switch 4/12 Administrator's Manual

In a stable fabric, frames are always delivered in order, even when the traffic between switches is shared
among multiple paths. However, when topology changes occur in the fabric (for example, if a link goes
down), traffic is rerouted around the failure, and some frames could be delivered out of order. Most
destination devices tolerate out-of-order delivery, but some do not.
Use of out-of-order frame-based delivery can minimize the number of frames dropped, while enabling
in-order delivery (IOD) gurantees that frames are either delivered in order or dropped. All HP B-series
switches enable IOD by default to ensure frames are delivered in order, as not all HP destination devices
can tolerate out-of-order frames.
To force in-order frame delivery across topology changes
1. Connect to the switch and log in as admin.
2. At the command line, enter the iodReset command.
This command can cause a delay in the establishment of a new path when a topology change
NOTE:
occurs; use it with care.
3. To confirm the In Order Delivery has been set, issue the iodShow command.
To restore out-of-order frame delivery across topology changes
1. Connect to the switch and log in as admin.
2. Enter the iodSet command at the command line.

Using Dynamic Load Sharing

The exchange-based routing policy depends on the Fabric OS Dynamic Load Sharing feature (DLS) for
dynamic routing path selection. When using the exchange-based routing policy, DLS is by default enabled
and cannot be disabled. In other words, you cannot enable or disable DLS when the exchange-based
routing policy is in effect.
When the port-based policy is in force, you can enable DLS to optimize routing. When DLS is enabled, it
shares traffic among multiple equivalent paths between switches. DLS recomputes load sharing when a
switch boots up or each time an E_Port goes offline and online, or a Fx_Port goes offline.
To check and set DLS
1. Connect to the switch and log in as admin.
2. Enter the dlsShow command to view the current DLS setting.
One of the following messages appears:
• "DLS is set" indicates that dynamic load sharing is turned on.
• "DLS is not set" indicates that dynamic load sharing is turned off.
• "DLS can not be changed with current routing policy" indicates that you are using the
exchange-based routing policy and you cannot enable or disable DLS.
3. Enter the dlsSet command to enable DLS or enter the dlsReset command to disable it.
switch:admin> dlsshow
DLS is not set
switch:admin> dlsset
switch:admin> dlsshow
DLS is set
switch:admin> dlsreset
switch:admin> dlsshow
DLS is not set
Fabric OS 5.2.x administrator guide 193