The Fibre Channel Protocol (FCP) supports access to Small Computer System Interface (SCSI) peripheral devices in the z/VM, z/VSE, and Linux on IBM z Systems environments. This is in contrast to FICON, the protocol which supports access to Extended Count Key Data (ECKD) peripheral devices.
FCP utilizes the Queued Direct Input/Output (QDIO) architecture, in similar fashion to the Open Systems Adapter (OSA) for Ethernet local area network (LAN) connectivity. Rather than using traditional channel programs, QDIO enables direct memory-to-memory transfers between the host and the channel.
FCP performance metrics
When a FICON channel is configured as CHPID type FCP, I/O information is made available relating to FCP performance (latencies) and FCP channel usage. Linux on z Systems can extract the hardware statistics (time spent in the fabric and time spent on the channel) to assist with the preparation of graphics and help analyze the performance and usage of FCP channels. FCP performance metrics applies to the FICON Express8S, FICON Express8, FICON Express4 and FICON Express2 features (CHPID type FCP). FCP performance metrics is supported on zEnterprise EC12, zEnterprise BC12, zEnterprise 196, zEnterprise 114, System z10, and System z9 servers with Linux on z Systems.
FCP performance increase for small block sizes
With the introduction of System z10, the Fibre Channel Protocol (FCP) Licensed Internal Code (LIC) was modified to help provide increased I/O operations per second for small block sizes. zEnterprise EC12, zEnterprise BC12, zEnterprise 196, and zEnterprise 114 continue to support this LIC.
Increased performance for the FCP protocol: A FICON Express8S feature, when defined as CHPID type FCP, conforms to the Fibre Channel Protocol (FCP) standard to support attachment of SCSI devices, to complement the classical storage attachment supported by FICON and zHPF channels.
In laboratory measurements, using FICON Express8S in a z196 with the FCP protocol for small data transfer I/O operations, FICON Express8S operating at 8 Gbps achieved a maximum of 92,000 IOs/sec, compared to the maximum of 84,000 IOs/sec achieved with FICON Express8 operating at 8 Gbps. This represents approximately a 10% increase and applies to reads, writes, and a read/write mix. Results on zEC12 and zBC12 are comparable.
In laboratory measurements, using FICON Express8S in a z196 with the FCP protocol and an internal driver supporting the hardware data router, executing a mix of large sequential read and write data transfer I/O operations, FICON Express8S operating at 8 Gbps achieved a maximum throughput of 1600 MB/sec (reads + writes) compared to the maximum of 770 MB/sec (reads + writes) achieved with FICON Express8 operating at 8 Gbps. This represents approximately a 108% increase. Results on zEC12 and zBC12 are comparable.
The FCP protocol is supported by z/VM, z/VSE, and Linux on z Systems.
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