80 Fabric OS Administrator’s Guide
53-1001763-02
Lossless Dynamic Load Sharing on ports
4

Lossless core

Lossless core works with the default configuration of the Brocade DCX and DCX-4S to prevent
frame loss during a core blade removal and insertion. This feature is on by default and cannot be
disabled. Lossless core has the following limitations:
•Only supported with IOD disabled which means Lossless core cannot guarantee in-order
delivery of exchanges.
•ICL limitations.
•Traffic flow limitations.

ICL Limitations

If ICL ports are connected during a core blade removal, then it is equivalent to removing external
E_Ports which cause I/O disruption on the ICL ports that have been removed.
If ICL ports are connected during a core blade insertion, then it is equivalent to adding external
E_Ports which may cause I/O disruption due to reroutes. Lossless DLS, if enabled, takes effect to
prevent I/O disruption.

Traffic flow limitations

The FA4-18 and FR4-18i AP blades, which are supported on the Brocade DCX and DCX-4S, may
continue to experience frame drops after core blade removal or insertion. The path between an
FC10-6, FA4-18, and FR4-18i blade and an FX8-24 blade, or vice-versa, will experience I/O
disruption because the FC10-6, FA4-18, and FR4-18i blades do not support this feature.

Configuring Lossless Dynamic Load Sharing

You configure Lossless DLS switch- or chassis-wide by using the dlsSet command to specify that no
frames are dropped while rebalancing or rerouting traffic.
1. Connect to the switch and log in using an account assigned to the admin role.
2. Enter the appropriate dlsSet command to enable or disable Lossless Dynamic Load Sharing.
switch:admin>dlsset --enable lossLess
switch:admin>dlsset --disable lossLess

Lossless Dynamic Load Sharing in Virtual Fabrics

Enabling Lossless Dynamic Load Sharing is optional on logical switches in a Virtual Fabric. If you
enable this feature, it must be on a per logical switch basis and can affect other logical switches in
the fabric.XISL use must be disabled for Lossless DLS to be enabled
Exchange-based Disabled No frame loss, but out of order frames may occur.
Exchange-based Enabled No frame loss and no out of order frames. Topology restrictions apply. Intended
for FICON environment.
TABLE 9 Combinations of routing policy and IOD with Lossless DLS enabled (Continued)
Policy IOD Rebalance result with Lossless DLS enabled