IBM eServer zSeries 990 Technical Guide

Chapter 8. Capacity upgrades 219

Considerations when installing additional books

During a z990 server upgrade, additional books can be concurrently installed. Depending on

the number of additional books in the upgrade and the customer’s I/O configuration, an STI

Rebalancing may be recommended for availability reasons. However the z990 STI

Rebalancing, via the STI Rebalance feature, requires STI recabling and results in a server

outage. It may also change ICB-4 PCHID numbers, requiring an I/O definition update.

8.7 Capacity planning considerations

The z990 servers represent a major evolution for the Series platform, extending the key

platform characteristics and embracing e-business on demand requirements.

The z990 has significant performance improvements over the previous z900 servers. The

z990 server includes enhanced processor and system designs, and also introduces new

building blocks, such as the multi-book structure.

z990 introduces a new microprocessor architecture exploiting the CMOS9S-SOI technology

while improving uniprocessor performance. A significant capacity and throughput increase

has been achieved with the introduction of:

򐂰 Up to 32 Processor Units as CPs, IFLs, ICFs, or zAAPs, for operating systems

򐂰 Up to eight Processor Units, as standard System Assist Processors (SAPs), for I/O

processing

򐂰 Up to 30 logical partitions

򐂰 Up to 256 GB of memory

򐂰 Up to 96 GBps of bandwidth for data communication via up to 48 Self-Timed Interconnect

(STI) host buses

򐂰 A new Channel Subsystem (CSS): four Logical Channel Subsystems (LCSSs) can exist

for horizontal growth, supporting up to 256 CHPIDs per CSS for a total of 1024 CHPIDs

per system

򐂰 Increased channel maximums for ESCON, FICON Express, and OSA-Express

򐂰 Three cryptographic features:

– New CP Assist for Cryptographic Function (CPACF)

– New PCIX Cryptographic Coprocessor (PCIXCC)

– PCI Cryptographic Accelerator (PCICA)

򐂰 Integrated Cluster Bus-4 (ICB-4), capable of up to 2 GBps

Some of the most important performance related topics are the balanced system design, the

superscalar processors, and the integrated hardware and system assists.

8.7.1 Balanced system design

One of the most important design objectives of a zSeries server is to build a balanced

system. This means a system with no specific constraints, where individual parts, such as

processor speed, memory bandwidth, and I/O bandwidth, are designed for the server’s best

performance and throughput.

The balanced system design is also based on the fact that no single component just by itself,

like processor frequency (expressed in GHz), can improve the system’s overall performance

for a wide range of workloads and applications.