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A New Performance Paradigm

zHPF Improves Upon Mainframe’s I/O Capabilities


IBM System z* High Performance FICON* (zHPF) is the most recent advance in optimizing mainframe I/O for storage devices. An open standard, the zHPF architecture has been adopted by all enterprise-class storage vendors for DASD attachment to System z10* and zEnterprise* servers.

Introduced in 2008 for the IBM DS8000* storage subsystem and System z10 servers with FICON Express4 channels, zHPF technology delivered several enhancements to transparently improve the performance and resilience of applications and middleware running on z/OS*. IBM has extended the value of the zHPF architecture to an increasing portion of z/OS workloads running on zHPF-capable hardware.

What is zHPF?

System z servers provide an infrastructure using standard I/O adapters, called host bus adapters (HBAs), for communicating over fiber channel (FC) storage area networks (SANs). This infrastructure provides robust hardware and system firmware to adapt the HBAs for the mainframe with the system assists needed to provide enterprise-class reliability, availability and serviceability (RAS). These assists help assure the server stability and data integrity transparently to the applications and middleware running on the server.

Over time, HBA vendors have added hardware assists that accelerate the execution of the Fiber Channel Protocol (FCP). However, z/OS technology requires support for the FICON protocol to deliver mainframe qualities of service and optimal execution of heritage software. A new I/O paradigm was required for System z to leverage hard-ware assists provided by HBA vendors.

This new paradigm is zHPF. It provides a bilingual channel protocol to storage subsystems. Channels and control units implementing zHPF must also support FICON, which is required to support existing I/O programs (called channel programs) used by client applications and ISV products. FICON is also required for channel programs that use conditional execution and exploit the presentation of intermediate status, such as those using program controlled interrupts (PCIs).

By dynamically choosing between zHPF and FICON, z/OS technology optimizes the execution of I/O requests. The zHPF open standard has been adopted by all enterprise-class vendors providing DASD storage for the main-frame. In its essence, zHPF leverages hardware assists provided by HBA vendors for the FCP transport while preserving enterprise-class qualities of service supported by FICON, including:

  • End-to-end data integrity checking, transparent to applications and middleware, between the System z processor and storage controller
  • In-band I/O measurements to facilitate capacity planning, autonomic workload management, problem determination and data placement for the exploitation of storage tiers
  • Efficient, high-performance execution at a distance for two- and three-site configurations, including Geographically Dispersed Parallel Sysplex* (GDPS*)
  • Autonomic workload management for I/O (Intelligent Resource Director), including dynamic assignment of I/O priority, management of HyperPAV aliases, and dynamic throttling of I/O start rates and bandwidth with Dynamic channel path identifier (CHPID) management
  • Rigorous I/O timeouts and timely detection of errors including lost frames
  • Fairness for I/O resource sharing and application of I/O priorities
  • First failure data capture for quick, root-cause identification of failures that can disrupt the workload
  • Identification of single points of failure in the I/O configuration
  • Real-time configuration checking to detect miscabling events and prevent data corruption
  • Investment protection with 100 percent backward compatibility for existing software

The zHPF architecture is a comprehensive set of System z I/O architecture and firmware enhancements, DS8000 family device architecture and firmware improvements, and z/OS function. It transparently provides dramatic improvements in I/O rates, bandwidth and I/O service times while preserving the qualities of service System z clients rely on to run their enterprises.

Harry M. Yudenfriend is an IBM Fellow with Systems and Technology Group, System z and Power who joined IBM in 1980. He was named an IBM Master Inventor in 2001 and has achieved his 33rd invention plateau.



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