HP AA979A - StorageWorks SAN Switch 2/8V, Administrator'S Manual, Page: 396 / 465

402 Configuring and monitoring FCIP tunneling
FC fastwrite over Fibre Channel ISLs
FC Fastwrite operates in Fibre Channel network topologies similar to the basic topology shown in
Figure 34 . FC Fastwrite provides accelerated speeds for SCSI Write operations over long distance Fibre
Channel ISLs. FC Fastwrite is supported in Fabric OS v5.3.x and later.
Figure 34 Typical network topology for FC Fastwrite
Platforms and OS requirements for FC Fastwrite
Fabric OS supports FC Fastwrite between two 400 MP Routers or two 4/256 SAN Directors with FR4-18i
blades connected by Fibre Channel ISLs. FC Fastwrite 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 FC Fastwrite flow to enable this feature.
How FC Fastwrite works
Figure 35 shows how FC Fastwrite works. Fastwrite provides a proxy target (PT) local to the initiator host,
and a proxy initiator (PI) local to the target storage device.
1. The initiator sends a write command.
2. The PT responds with a Transfer Ready, enabling the host to send more data.
3. The target device processes the write command, and sends a Transfer Ready to solicit more data. The PI
intercepts the Transfer Ready, and begins sending data received from the host.
4. The PI continues to stage data received from the initiator, respond locally to Transfer Ready, and send
the data to the target device until the target device sends an FCP_RSP.
Figure 35 How FC Fastwrite works