AIX — which stands for Advanced Interactive eXecutive — is a POSIX-compliant and X/Open-certified Unix operating system introduced by IBM in 1986. While AIX is based on UNIX System V, it has roots in the Berkeley Software Distribution (BSD) version of Unix as well. Today, AIX has an abundance of both flavors (you can go with chocolate one day and vanilla the next), providing another reason for its popularity.
From its introduction in 1969 and development in the mid-1970s, Unix has evolved into one of the most successful operating systems to date. The roots of this operating system go as far back as the mid-1960s, when AT&T’s Bell Labs partnered with General Electric and the Massachusetts Institute of Technology (MIT) to develop a multi-user operating system called Multics (which stood for Multiplexed Information and Computer Service). Dennis Ritchie and Ken Thompson worked on this project until AT&T withdrew from it. The two eventually created another operating system in an effort to port a computer game that simulated space travel. They did so on a Digital Equipment Corporation (DEC) PDP-7 computer, and they named the new operating system Unics (for Uniplexed Information and Computing Service). Somewhere along the way, “Unics” evolved into “Unix.”
AIX was the first operating system to introduce the idea of a journaling file system, an advance that enabled fast boot times by avoiding the need to perform file system checking (fsck) for disks on reboot. AIX also has a strong, built-in Logical Volume Manager (LVM), introduced as early as 1990, which helps to partition and administer groups of disks.
Another important innovation was the introduction of shared libraries, which avoided the need for an application to statically link to the libraries it used. The resulting smaller binaries used less of the hardware RAM to run and required less disk space for installation.
IBM ported AIX to its RS/6000 platform of products in 1989. The release of AIX Version 3 coincided with the announcement of the first RS/6000 models. At the time, these systems were considered unique in that they not only outperformed all other machines in integer compute performance but also beat the competition by a factor of 10 in floating-point performance.
Version 4, introduced in 1994, added support for symmetric multiprocessing (SMP) with the first RS/6000 SMP servers. The operating system evolved until 1999, when AIX 4.3.3 introduced workload management (WLM). In May 2001, IBM unveiled AIX 5L (the L stands for “Linux affinity”), coinciding with the release of its POWER4 servers, which provided for the logical partitioning of servers. In October of the following year, IBM announced dynamic logical partitioning (DLPAR) with AIX 5.2.
The latest update to AIX 5L, AIX 5.3 (introduced in August 2004), provided innovative new features for virtualization, security, reliability, systems management, and administration. Most important, AIX 5.3 fully supported the Advanced Power Virtualization (APV) capabilities of the POWER5 architecture, including micropartioning, virtual I/O servers, and symmetric multithreading (SMT). Arguably, this was the most important release of AIX in more than a decade, and it remains the most popular (as of this writing). That is why we’ll primarily focus on AIX 5.3 for the purposes of this book.
IBM announced AIX 6-Beta in May 2007 and formally introduced AIX 6.1 in November 2007. Major innovations of AIX 6.1 include workload partitions (WPARs), which are similar to Solaris containers, and Live Application Mobility (not available with Solaris), which lets you move the partitions without application down time. Chapter 16 discusses performance monitoring and tuning on AIX 6.1.
AIX Market Share
AIX celebrated its 20th anniversary in January 2006, and it appears to have an extremely bright future in the Unix space. IBM’s AIX has been the only Unix that increased its market share through the years, and IBM continues to own the market space for Unix servers. Most of the Unix growth at this time stems from IBM.
AIX has benefited from the many hardware innovations that the POWER platform has introduced through the years, and it continues to do so. IBM has also made good decisions around its Linux strategy. Linux, supported natively on the POWER5, more or less complements, rather than competes with, AIX on the POWER architecture.