Trends > AIX

WPAR Power

AIX 6 workload partitions explained

The July release of the IBM* AIX* 6 Open Beta OS introduced workload partitions (WPARs), an exciting new feature with the potential to improve administration efficiency and assist with server consolidation. I've been impressed with its ease of deployment and potential cost savings.

WPARs carve a single instance of the AIX OS into multiple virtual instances, allowing for separate "virtual partitions." This capability allows administrators to deploy multiple AIX environments without the overhead of managing individual AIX images. This could be useful at sites with many AIX instances.

The open beta can run on any IBM System p* platform that's based on POWER4*, PPC970, POWER5* or POWER6* processors. (For the purposes of my testing, I installed the beta onto a POWER4 p650 LPAR.) You can download the open beta from IBM's AIX 6 Open Beta Web site.

Workload Partitions

A WPAR is a virtualized OS environment within an instance of AIX. This single instance of AIX is known as the global environment and is really no different from a standalone instance of the OS. The global environment can be hosted within an LPAR, which can consist of either dedicated or shared processors and virtual or physical I/O. The global environment owns all system resources (CPU, memory, I/O). From the global environment you can create multiple WPARs; 8,192 is the theoretical maximum. Each WPAR is a secure and isolated AIX environment: Workload in one WPAR can't interfere with workload in another. See Figure 1.

The AIX environment within a WPAR is built upon a shared global (read-only) /usr and /opt filesystem. These shared filesystems enable the virtualization of a single instance of AIX. All WPARs share the same global AIX kernel, which means they also share the same level of AIX. This makes maintenance easier as you only have one AIX instance to update.

From an application perspective, most software will function within a WPAR without modification. The application will function as if it were running in its own "real" instance of AIX. Applications within a WPAR have private execution environments and are isolated from other processes outside the WPAR.

There are two types of workload partitions. A system WPAR resembles a complete instance of AIX. It has its own processes and daemons (e.g., init, inetd, cron, etc.). It's similar to a change root (chroot) environment with access to normal AIX system files. It's created under a base directory (default /wpars/wparname), which is the root of the chroot AIX environment.

An application WPAR is a lightweight environment suitable for executing one or more application processes and is beneficial if you need to run multiple isolated applications but don't require a complete AIX environment. WPARs are attractive for several reasons:

• You can consolidate multiple workloads to one AIX image yet maintain the security and isolation for each workload. You may have several development environments that all use the same application software and level of AIX but don't require their own physical LPAR. Using WPARs you could build one LPAR, then deploy several WPARs for each development stream without separate hardware resources and images of AIX.
• Quick creation for testing is possible without additional hardware. If an environment is needed quickly you could create a WPAR for testing within a few minutes.
• WPARs may help reduce administration overhead. You no longer must upgrade multiple instances of AIX, only the global instance, which updates all WPARs.
• One application installation can support multiple WPARs, reducing the total number of installations. With WPARs, you must only install DB2* once in the global environment and every WPAR on the system can access it.
• You can separate administrative roles based on WPARs. WPARs allow delegation of root privileges to a person within a particular WPAR. You could provide a user root access to a specific WPAR to perform some administrative task. Even with root access in this WPAR, the user can't execute privileged commands within other WPARs or the global environment.

Next page: >>