IBM 990 - Manual (Page 231)

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.