Richard K. Errickson

The integrated cluster bus for the IBM S/390 parallel Sysplex

IBM has developed a new S/390® Parallel Sysplex® coupling interface for the G5 server called the Integrated Cluster Bus (ICB). This interface improves the coupling efficiency by greatly reducing message-passing latency. Using the transport layer of the S/390 self-timed interface (STI) introduced in the G3 server, ICB adds channel function to the hub chip to allow a more direct interconnection between S/390 servers. This new channel has the same function as the present intersystem channel (ISC), but because it is integrated into the hub chip and therefore requires no additional components, its reliability is much better than that of the ISC. Since the ISC transmits data at a peak rate of 106 MB/s over distances exceeding ten kilometers and the ICB transmits data at a peak rate of 333 MB/s at distances of ten meters, the ISC is still required for the more geographically dispersed Parallel Sysplexes, whereas the ICB is well suited to the machine room, where multiple servers can be interconnected by ten-meter cables. This paper describes the design approach for the ICB. It describes the fundamental message-passing requirements of the Parallel Sysplex and how they are implemented in very complex yet compact hardware in the servers hub chip.

Coupling I/O channels for the IBM eServer z900: reengineering required

The IBM eServer z900 introduces new Parallel Sysplex® coupling channels that satisfy evolving requirements in a way that minimizes product and development costs. Their design also provides backward compatibility with earlier S/390® models, spans all three coupling channel design points, and anticipates future end-of-life technology issues. The original intersystem channel (ISC) design was improved, and new features added, but the core chips were retained. This paper describes the efforts that led to the improved design.

IBM Parallel Sysplex design for the IBM z196 system

The coupling adapter hub of an IBM System z® server is a key component for the IBM System z Parallel Sysplex®. The hub is built to exchange messages between systems in a highly efficient manner. This paper describes the latest generation of high-fanout and low-latency coupling adapter cards, the associated firmware, and a new protocol. As in the z10® system, there is a long-range and a short-distance card. The coupling adapter for zEnterprise® 196 (z196) is based on the z10 infrastructure (InfiniBand® link layer), with the internal transport engine for message handling completely redesigned to support the new protocol and improve connectivity, latency, and throughput. In addition to enabling the new adapters functionality, the Parallel Sysplex support firmware has several significant enhancements in a number of functional areas. Connectivity and utilization are improved through the ability to define more channels and more concurrent connections (message buffer sets) for each channel. Through a combination of hardware and firmware protocols, response time for messages at a short distance is significantly improved. Finally, new methods are presented that support efficient presilicon and postsilicon functional and performance verification.

Redundant I/O interconnect

The outstanding reliability, availability, and serviceability (RAS) characteristics of IBM mainframe computers are among the features that gained the IBM eServerTM family its reputation as a leading platform for business-critical applications. The aim now is to further improve IBM System z9® RAS by introducing redundant I/O interconnect (RII) as a building block of enhanced book availability and recovery scenarios. RH provides a means of maintaining I/O connectivity during planned or unplanned outages in a way that is transparent to the operating system and customer applications. The mechanism that meets this requirement is the provision of an alternate path to the I/O cage, which provides high-bandwidth I/O slots to enable a higher number of I/O ports per card. This paper discusses the I/O subsystem hardware and firmware aspects of RII.