LPAR for AS/400: you have to consolidate to accumulate

LPAR for AS/400 was announced with V4R4 of OS/400. However, many users say it is too inflexible for them to adopt at present. Do...

LPAR for AS/400 was announced with V4R4 of OS/400. However, many users say it is too inflexible for them to adopt at present. Do you subscribe to this view?


LPAR for AS/400 was announced with V4R4 of OS/400. However, many users say it is too inflexible for them to adopt at present as the processing capacity of each partition has to be the power of one or more of the processors of the large, multi-processor machines and so doesn't fit their processing requirements. Put simply, to create the number of the partitions they want means buying a far more powerful machine than they need. When will the ability to partition by power requirement (i.e. using part of the power of an individual processor card ) be introduced and how?


Logical Partitioning allows multiple copies of OS/400 to run in a single SMP machine. This capability is supported on the SMP processors on the 6xx, Sxx, and 7xx models of AS/400, writes Nigel Adams. Since this first became available in May 1999, when Version 4 Release 4 of OS/400 shipped, it has been used by many customers as a means of AS/400 server consolidation.

Consultant reports have shown that there is a strong trend amongst IT users towards server consolidation to provide greater manageability of servers, reduce operation costs, and also to improve performance and the service offered to users. Server consolidation in this case could be described as optimising the IT infrastructure by integrating, and therefore simplifying, multiple computer architectures, computing sites, applications, data, and staff skills. The result of this consolidation is reduced costs and improved efficiency, in delivering IT services.

Over the last few years, the dramatic increase in the power of the AS/400 has meant that multiple systems and workloads that previously ran on a number of separate AS/400s, can be handled by a single machine.

This is illustrated by the fact that the Commercial Processing Workload (CPW) rating of the most powerful AS/400 in the range has increased from 177.4 on the Model 320 - the last Cisc Model of AS/400 - to 4550 today on the 12-way Model 740. The introduction of Logical Partitioning has further promoted the ability to consolidate multiple AS/400s onto a single system.

There are a number of benefits that flow from using Logical Partitioning as a means of doing server consolidation:

  • Customised partition performance - independent partitions each have their own processors, memory, and disk as appropriate, depending upon workload.

  • Multi-tiered applications - application serving and database serving can be supported by separate partitions within a single machine.

  • Consolidation of multiple servers - lower operational staff costs from having fewer systems to manage. This can also include consolidation of systems that are widely dispersed geographically as each partition within a server can have its own system values, language and time setting.

  • High speed data replication - replicate data from one partition to another using the internal high speed bus communications capability. This will not give the higher levels of availability offered by replicating to a second system, but it can be used to provide a second read-only copy of the data to be used by appropriate applications, such as Business Intelligence, as well as allowing improved save operations.

  • Application development and test environment - the ability to do such work in separate partitions, while also running business critical applications in the same AS/400.

The software capability to do Logical Partitioning is a standard part of OS/400 Version 4 Release 4 - there is no software charge involved. As mentioned in the question, each partition must have at least one processor allocated to it; and also memory is allocated to specific partitions.

Processor and memory resources can be moved between partitions, but this requires a re-IPL of the partitions involved. Input/Output Processors (IOPs) can be dynamically moved without a re-IPL between partitions allowing resources such as tape drives, CD-Rom and communications adapters to be utilised by any individual partition as appropriate. The exceptions to this are resources attached to Disk IOPs and to the Multi-Function IOP (MFIOP).

Communications between logical partitions can either be handled externally using Lan/Wan adapters in the normal way; or internally using virtual Opticonnect. The latter allows high speed communications between partitions, using the bus bandwidth; and will clearly give superior performance.

Clearly, although the current implementation of Logical Partitioning offers a great deal in terms of Server Consolidation, it would be even more attractive if the resources described above could be dynamically moved between partitions, and also if individual processors could be split amongst multiple partitions, thus increasing the granularity with which processing power can be distributed between partitions.

Unfortunately I am not in a position to discuss when this capability might become available, but I can certainly say that both of these requirements are well understood by the developers, and that AS/400 investments in Logical Partitioning will continue in future releases of OS/400. Already, with the initial implementation of Logical Partitioning offered with Version 4 Release 4, the AS/400 already offers a very powerful capability which compares very favourably with comparable offerings as a means of consolidating multiple systems onto a single server.

Read more on Server hardware