Dell Brocade G620 Brocade 8.0.1 Fabric OS Administratiors Guide - Page 122

Lossless Dynamic Load Sharing in Virtual Fabrics, How DLS affects other logical switches in the fabric

Page 122 highlights

Routing Traffic To configure Lossless Dynamic Load Sharing, complete the following steps. 1. Connect to the switch and log in using an account with admin permissions. 2. Enter the appropriate dlsSet command to enable or disable Lossless Dynamic Load Sharing. switch:admin> dlsset --enable -lossless switch:admin> dlsset --disable -lossless NOTE To enable lossless on the whole chassis when multiple logical switches exist, you must enable lossless on each logical switch independently or use the fosexec --fid all -cmd dlsset command. Lossless Dynamic Load Sharing in Virtual Fabrics Enabling Lossless Dynamic Load Sharing is optional on logical switches in Virtual Fabrics. If you enable this feature, it must be on a perlogical switch basis and can affect other logical switches in the fabric. How DLS affects other logical switches in the fabric On a Brocade DCX 8510 platform, logical switch 1 consists of ports 0 through 5 in slot 1. Logical switch 2 consists of ports 6 through 10 in slot 1. The Lossless DLS feature is enabled on logical switch 1. Because ports 0 through 5 in slot 1 belong to a logical switch where Lossless DLS is enabled, the traffic in logical switch 2 is affected whenever traffic for logical switch 1 is rebalanced. ATTENTION Although Lossless DLS is enabled for a specific logical switch, you must have chassis-level permissions to use this feature. The effect on logical switch 2 is based on the configuration on logical switch 2: ∙ If logical switch 2 has IOD enabled (iodSet only), IOD is enforced. ∙ If logical switch 2 has Lossless DLS enabled, traffic is paused and resumed. ∙ If logical switch 2 has no IOD (iodReset ), traffic is paused and resumed. To avoid this behavior, it is recommended to define your logical switches as follows: ∙ Define logical switches that require Lossless DLS at the blade boundary. ∙ Define logical switches that require Lossless DLS only using supported blades. For example, do not use blades that support IOD, but do not support Lossless DLS. For more information on Virtual Fabrics and chassis-level permissions, refer to Managing Virtual Fabrics on page 267. Two-hop Lossless DLS route update Certain fabric topology changes may affect the Shortest Path First results that lead to rebalance operations, and thus change the paths utilized. During these rebalance operations, even if the lossless DLS setting is enabled, route updates caused by fabric shortest path changes may result in I/O disruptions and/or out-of-order frame delivery. Route updates are not done globally across all switches at the same time. A new path may be used before the later switches are ready. Lossless DLS supports rebalance operations after events that affect redundancy within a hop but do not cause fabric shortest path changes. Lossless DLS can only ensure that the local switch updates are performed in the required manner. Lossless DLS cannot ensure that a downstream domain has completed its rebalancing operations prior to a new path being used. The Two-hop enhancement to Lossless DLS extends the lossless route update capabilities to support the addition of a new hop between switches. When a new link is added between two switches where one was not there previously, the new link is likely to cause changes to the shortest path results. The Two-hop enhancement to Lossless DLS ensures that the route updates happen on the local switches of the Brocade Fabric OS Administration Guide, 8.0.1 122 53-1004111-02

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To configure Lossless Dynamic Load Sharing, complete the following steps.
1.
Connect to the switch and log in using an account with admin permissions.
2.
Enter the appropriate
dlsSet
command to enable or disable Lossless Dynamic Load Sharing.
switch:admin> dlsset --enable -lossless
switch:admin> dlsset --disable -lossless
NOTE
To enable lossless on the whole chassis when multiple logical switches exist, you must enable lossless on each logical
switch independently or use the
fosexec --fid all -cmd dlsset
command.
Lossless Dynamic Load Sharing in Virtual Fabrics
Enabling Lossless Dynamic Load Sharing is optional on logical switches in Virtual Fabrics. If you enable this feature, it must be on a per-
logical switch basis and can affect other logical switches in the fabric.
How DLS affects other logical switches in the fabric
On a Brocade DCX 8510 platform, logical switch 1 consists of ports 0 through 5 in slot 1. Logical switch 2 consists of ports 6 through 10
in slot 1. The Lossless DLS feature is enabled on logical switch 1. Because ports 0 through 5 in slot 1 belong to a logical switch where
Lossless DLS is enabled, the traffic in logical switch 2 is affected whenever traffic for logical switch 1 is rebalanced.
ATTENTION
Although Lossless DLS is enabled for a specific logical switch, you must have chassis-level permissions to use this feature.
The effect on logical switch 2 is based on the configuration on logical switch 2:
If logical switch 2 has IOD enabled (
iodSet
only), IOD is enforced.
If logical switch 2 has Lossless DLS enabled, traffic is paused and resumed.
If logical switch 2 has no IOD (
iodReset
), traffic is paused and resumed.
To avoid this behavior, it is recommended to define your logical switches as follows:
Define logical switches that require Lossless DLS at the blade boundary.
Define logical switches that require Lossless DLS only using supported blades. For example, do not use blades that support
IOD, but do not support Lossless DLS.
For more information on Virtual Fabrics and chassis-level permissions, refer to
Managing Virtual Fabrics
on page 267.
Two-hop Lossless DLS route update
Certain fabric topology changes may affect the Shortest Path First results that lead to rebalance operations, and thus change the paths
utilized. During these rebalance operations, even if the lossless DLS setting is enabled, route updates caused by fabric shortest path
changes may result in I/O disruptions and/or out-of-order frame delivery. Route updates are not done globally across all switches at the
same time. A new path may be used before the later switches are ready.
Lossless DLS supports rebalance operations after events that affect redundancy within a hop but do not cause fabric shortest path
changes. Lossless DLS can only ensure that the local switch updates are performed in the required manner. Lossless DLS cannot
ensure that a downstream domain has completed its rebalancing operations prior to a new path being used. The Two-hop enhancement
to Lossless DLS extends the lossless route update capabilities to support the addition of a new hop between switches.
When a new link is added between two switches where one was not there previously, the new link is likely to cause changes to the
shortest path results. The Two-hop enhancement to Lossless DLS ensures that the route updates happen on the local switches of the
Routing Traffic
Brocade Fabric OS Administration Guide, 8.0.1
122
53-1004111-02