Brocade Fabric OS Documentation Updates - Supporting Fabric OS v6.4.x (53-1002063-09, August 2012)

50 Fabric OS Documentation Updates

53-1002063-09

Documentation updates for Fabric OS v6.4.0 and v6.4.1

FC Fast Write (FCFW) concepts

FCFW operates in Fibre Channel network topologies similar to the basic topology shown in Figure 1.

FCFW provides accelerated speeds for SCSI Write operations over long distance Fibre Channel ISLs

implemented through the FC-FC Routing Service (FRS) rather than FCIP

FIGURE 1 Typical network topology for FCFW

Platforms and OS requirements for FCFW

Fabric OS supports FCFW between two Brocade 7500 routers or two FR4-18i blades connected by

a Fibre Channel network. FCFW is a new feature beginning with Fabric OS release v5.3.0. There is

no backwards compatibility with previous releases. Release v5.3.0 or later is required in the

switches/blades at both ends of the FCFW flow to enable this feature.

NOTE

FCFW and FCIP tunnels cannot be used together on the same 7500 or FR4-18i blade.

Constraints for FCFW

Consider the following constraints when configuring FCFW:

• FCFW disables the local Ethernet ports (ge0 and ge1), making it impossible to configure FCFW

and FCIP tunnels on the same 7500 or FR4-18i blade.

• FCFW does not work in FICON environments.

• FCFW flows may be routed to another 7500 or FR4-18i blade on the FC network. This 7500 or

FR4-18i blade may have active FCIP tunnels over an IP network. FCFW flows may be passed

through the FCIP tunnel, but only if the FCIP fastwrite option is disabled on the tunnel.

• FCFW does not support loop device configurations for more than one device.

How FCFW works

FCFW eliminates the latency inherent in sending a Transfer Ready back to the initiator when writing

data across ISLs to geographically distant target devices. FCFW provides a proxy target (PT) local to

the initiator host, and a proxy initiator (PI) local to the target storage device. Figure 2 shows how

FCFW works.