LPAR Pre-Flight Check
Logical partitioning (LPAR) has been available in the computing industry for many years. IBM introduced it for S/370s in 1988 and for iSeries systems in 1999. Early partitioning on S/370s involved physical partitioning with distinct hardware boundaries. Today, LPAR provides for an environment that allows the logical sharing of hardware resources among partitions. Essentially, LPAR enables users to separate iSeries hardware into two or more logical systems. Each of these logical systems is called a partition and operates as an independent system with its own hardware and software resources. This allows the creation of a separate environment, which includes its own level of the OS, user access, security, applications, time zones, etc.
LPAR offers many benefits. One of the driving forces behind companies consolidating iSeries servers is to reduce costs by sharing hardware resources.
Hardware resource sharing can be as simple as using one tape drive between partitions for backup and restore activities. Others create complex scenarios for moving processing resources, such as CPU or memory, among various partitions based on application requirements, time of day, week or month, or processing workloads. Regardless of why companies share the resources of a partitioned system, they can benefit by effectively using system resources to provide a lower total cost of ownership.
So, youve investigated LPAR and your company has decided its ready to take flight. What do you do now? If youre planning to consolidate servers, you must carefully analyze both your hardware and software needs. "LPAR Planning Considerations" provides a list of software/hardware areas that should be considered as you plan for an LPAR environment. Lets examine each individually.
LPAR Hardware Considerations
IBM provides the LPAR Validation Tool (LVT) to help you plan your hardware needs. The GUI utility helps you design the physical layout of a partitioned system that stays within the bounds of LPAR hardware configuration recommendations. A word of caution when using the LVT: the validation of your configuration doesnt guarantee that youve designed the most economical layout. If youll be partitioning an older AS/400 system, IBM provides LPAR planning worksheets, which can be used to manually define and configure system needs. Neither of these can be considered absolute methods of defining final system configurations; rather, they should be used as a guide in the order/validation process.
Lets say you have two small Model 720s that you wish to move to one 810 with three partitions. As you define the features to order, consider minimum hardware requirements, additional hardware necessary to implement LPAR, replacement hardware requirements or upgrade for 720 to 810 and LPAR configuration.
At a minimum, each partition on your system must have the following:
- 256 MB memory for the primary partition; 128 MB memory for secondary OS/400* partitions and 64 MB for Linux partitions
- Load source disk unit for OS/400 partitions
- Console (e.g., IOP/IOA for console: twinax, Operations Console or LAN) for OS/400 partitions
- Available CD-ROM (recommended)
- 0.25 of a processor or more (depending on OS/400 and hardware levels)
These are the minimum partition requirements aside from any additional business requirements for each of your partitions. How do you go about defining what you really need? Both the LVT and the planning worksheets can be of use as you design your partition configurations. The planning worksheets list various items that you should take into account for each partition. However, they dont address resource sharing among partitions. To create the most economical system design using the LVT requires extensive knowledge of iSeries hardware and the ability to design the tower/bus layout based on card placement rules and limitations. As you work with the LVT, it presents error messages that warn you of missing features and potential problems. The final requirements used to design your plan in the LVT will be based on the needs listed on the planning worksheets, your configuration choices and any additional LPAR-related hardware.
You must decide whether the primary partition's sole purpose is to manage the LPAR environment or to use the primary partition as a "working" primary.
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