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AIX EXTRA: Using Dynamic LPAR in AIX 5L v5.2

Are you tired of server sprawl resulting from different OS levels and patch sets required by your application vendors? Or how about underutilized system resources needed for periodic, short-term production workload peaks? Or user-acceptance test environments that are idle for extended periods of time? Dynamic logical partitioning (DLPAR) features of the IBM eServer pSeries platform can help reduce the headaches and costs of running large complex UNIX environments.

Many pSeries platforms support LPAR. An LPAR-capable server can be carved up into a number of smaller logical machines. These smaller machines can be sized and configured to meet the specific workload requirements of the applications that they host.

Partitioning technology from other vendors today relies on various levels of "physical partitioning" of platform hardware. Physical partitioning places constraints on the size, physical slot locations and types of resources that can be allocated to a system partition. In contrast, IBM LPAR technology allows for the construction of partitions from the entire pool of platform resources--processor (in whole processors increments today), memory (in 256 MB increments) and interface cards. The ability to create these partitions allows system managers to provision and manage their hardware assets to maximize the cost effective use of their platform investment.

To understand the basics of LPAR on the pSeries server, it's use useful to step back and look at some of the major building blocks of an LPAR environment (see Figure 1). An LPAR-capable platform is based on the POWER4 processor or later--supported on servers such as the p690, p670 and p630--and runs microcode that is at least up to October 2002. The platform must also have the LPAR Hypervisor, a feature of the system firmware that creates LPARs and allocates or reallocates hardware resources to the LPAR.

Finally, the Hardware Management Console (HMC), which is a platform that's external to the pSeries server, is key. It sends commands to one or more pSeries servers to query and/or instruct the LPAR Hypervisor how to allocate, reallocate or release hardware resources to/from partitions. The HMC also provides a GUI for ease of LPAR administration and has a command line interface (CLI) for scripted configuration requests to the hypervisor. The CLI facilitates the automation of tasks and schedules and allows the administrator to reduce the amount of manual intervention required for resource management in the environment.

Dynamic LPAR
DLPAR, a feature of the LPAR environment on the pSeries platform, allows the allocation and de-allocation of resources--CPU, memory and interfaces--to meet the environment's capacity requirements. However, not all current OS environments support the ability to change the hardware configuration on the system without impacting environment availability.

While we can load and use a variety of AIX 5L v5.1, v5.2 and Linux OSs in LPARs on the pSeries server, only AIX 5L v5.2 supports DLPAR. AIX 5L can accept the allocation and de-allocation of processor and memory resources to the operating environment transparently and without impacting OS availability or causing an application outage.



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