DB2 Integrated Cluster Environment Deployment Guide

34 DB2 Integrated Cluster Environment Deployment Guide

2.1 Platform

DB2 UDB is available for a variety of Linux platforms; however, at the time of

writing, most DB2 Integrated Cluster Environment configurations have been

mainly tested and deployed on two platforms: IA32 and AMD64. By IA32 we are

referring to 32-bit Intel processor architecture, also generically known as x86.

And AMD64 refers to AMD's technology that extends the x86 platform to 64-bits,

hence generically called x86-64.

We limit discussion to these two architectures (x86 and x86-64), as they are the

most commonly used for Linux clusters, primarily due to their compelling

“price/performance” characteristics. With the growing appeal of Linux on IBM

POWER™ technology, future DB2 Integrated Cluster Environment offerings

based on IBM servers with PowerPC® chips may also be introduced. It is

possible to extend and apply many of the clustering concepts outlined in this

document to other Linux platforms.

It should be noted that the overall solution could be a hybrid one involving both

32-bit and 64-bit servers and clients; however, a single DB2 database can only

be partitioned across servers belonging to the same platform. In fact, all of the

servers in a database cluster should be running the same levels of the Linux

distribution and DB2 UDB.

2.1.1 IA32 (and x86)

When most people think about Linux, the 32-bit Intel environment is the default

and the most popular choice for deployment today. Among the available Linux

platforms, this platform is deemed to be the most mature, offers the largest range

of industry-standard (“commodity”) servers, and has the widest availability of

applications and utilities. DB2 UDB has been ported to this platform since 1998.

In addition to DB2 UDB, a large number of other add-on DB2 components and

extenders are available for this platform.

However, the drawback of this platform is the address limitation inherent in 32-bit

architectures. Processes in this environment can only directly address four

gigabytes of memory, which limits database shared memory area to a default of

about 1.7 gigabytes (and up to 2.5 gigabytes on certain Linux distributions). The

shared memory area is where database buffer pools and sort heaps are kept and

are critical to database performance. While it is possible to address more than

four gigabytes on 32-bit operating systems using memory extensions such as

PAE and AWE or though in-memory file systems, DB2 UDB has chosen not to

utilize these on Linux due to the performance overhead of these methods and

availability of several 64-bit Linux platforms.