Service Manual

Fabric OS 7.4.0a Release Notes v2.0 Page 49 of 53
ALL
ALL ALL
ALL to re-balance the E_Port load on a particular logical switch or on all the logical switches, without waiting for
a topology change to occur.
When the Dynamic Load Sharing (DLS)
Dynamic Load Sharing (DLS) Dynamic Load Sharing (DLS)
Dynamic Load Sharing (DLS) is disabled, Lossless Dynamic Load Sharing (DLS)
Lossless Dynamic Load Sharing (DLS) Lossless Dynamic Load Sharing (DLS)
Lossless Dynamic Load Sharing (DLS) is not supported and
the E_port Balance Priority
E_port Balance Priority E_port Balance Priority
E_port Balance Priority feature also gets disabled; but the E_port Balance
E_port BalanceE_port Balance
E_port Balance Priority
Priority Priority
Priority can be enabled even if
the DLS is in Off
Off Off
Off state.
The E_port balance priority is supported on the following z Systems qualified platforms at FOS 7.4.0a:
• Brocade DCX Backbone
• Brocade DCX-4S Backbone
• Brocade DCX 8510-4 Backbone
• Brocade DCX 8510-8 Backbone
• Brocade 7800
• Brocade 7840
To enable or disable E_port balance priority , perform the following steps.
1. Open the Switch Administration
Switch Administration Switch Administration
Switch Administration window.
2. Select the Routing
Routing Routing
Routing tab.
3. Select On
On On
On in the E
EE
E-
--
-port Balance Priority
port Balance Priority port Balance Priority
port Balance Priority area to enable E_Port load balance, or select Off
Off Off
Off to disable E_Port
load balance.
• Clicking the Rebalance
Rebalance Rebalance
Rebalance button will perform E_Port balancing on the current logical switch only and clicking
the Rebalance All
Rebalance All Rebalance All
Rebalance All button will perform E_Port balancing on all the logical switches available.
4.
4.4.
4. Click Apply
ApplyApply
Apply, and then click OK.
OK.OK.
OK.
Forward Error Correction (FEC) for FICON Express16S
With the FICON Express16S generation of features, IBM z Systems added Forward Error Correction (FEC)
capabilities to the Fibre Channel link protocol. FEC allows FICON channels to operate at higher speeds, over
longer distances, with reduced power and higher throughput, while retaining the same reliability and
robustness that FICON has traditionally been known for.
FEC is a technique used for controlling errors in data transmission over unreliable or noisy communication
channels. The technique has the sender encode messages in a redundant way by using an error-correcting
code (ECC). The redundancy allows the receiver to detect a limited number of errors that might occur anywhere
in the message and often corrects these errors without retransmission. FEC gives the receiver the ability to
correct errors without needing a reverse channel to request retransmission of data, but at the cost of a fixed,
higher forward channel bandwidth.
With FEC enabled, errors that might have started to show up with the new faster link speeds can likely be
corrected by the error correction technology in the optical transmit/receive ports. End users should see fewer
I/O errors, thus easing the transition to the new link technologies, reducing the potential impact to any
production workloads by I/O errors. For latency reduction, the entire path (end-to-end) needs to run at 16 Gbps
link speed. Likewise, each link, the entire path from the channel through the switch ports to the storage
subsystem, should be protected by an FEC-capable link to minimize the risk of I/O errors.
• Though FEC capability is generally supported on Condor3 (16G capable FC) ports when operating at either
10G or 16G speed, it is not supported with all DWDM links. Hence FEC may need to be disabled on
Condor3 ports when using DWDM links with some vendors by using portCfgFec command. Failure to
disable FEC on these DWDM links may result in link failure during port bring up. Refer to the Brocade
Fabric OS 7.x Compatibility Matrix for supported DWDM equipment and restrictions on FEC use.