AIX 5.2 provides dynamic partitions, other tweaks

Works with Power4

ComputerWire: IT Industry Intelligence

IBM Corp will today roll out the software that will enable its Power4-based AIX servers to make use of dynamic logical partitions. These have been available for decades on its mainframes and since 1999 on its AS/400-iSeries line,

writes Timothy Prickett Morgan


The dynamic logical partitioning support which is built into AIX works in conjunction with IBM's Power4-based servers, which have electronics that make it easier to make partitions work than is possible on prior generations of pSeries and RS/6000 Unix servers. AIX 5L version 5.2 also includes a number of other technologies and tweaks that make it a better operating system than AIX 5.1.

In theory, logical partitions could have been supported on Pulsar, I-Star, and S-Star RS/6000 and pSeries servers, a statement that is based on the fact that these same servers that bear the RS/6000 and pSeries monikers are also the same basic electronics complexes that are sold under the AS/400 and iSeries brands and which have very fine-grained dynamic logical partitions that allow fractions of processors, portions of memory, and slices of I/O devices to be configured as a virtual machine running either OS/400 or Linux. The word that we have heard for years is that the same team of microcode programmers who brought LPARs to the OS/400 were working as quickly as possible to bring it to AIX. IBM's Unix variant, which is based on the Mach Unix kernel from Carnegie Mellon University, is very different from the home-grown kernel in OS/400. So weaving LPAR support into AIX has been problematic. In February 1999, OS/400's logical partitions were only set at the CPU level, and they were not dynamic. With OS/400 V5R1 in April 2001, IBM made iSeries partitions dynamic, offered granularity on processors down to 1% of a CPU for a single partition (with a maximum of four LPARs per processor), and allowed partitions to be configured with Linux.

The dynamic logical partitioning that debuts in AIX 5L version 5.2 is based on a single-CPU granularity like the early OS/400 LPAR support, but is dynamic unlike the early OS/400 logical partitions. Processors, I/O adapters, and memory cards can be added to or removed from AIX LPARs without rebooting the server. A single AIX partition needs one processor, one I/O adapter, and 256MB of main memory to work.

These partitions can run AIX 5.1, AIX 5.2, or Linux. IBM can slice its top-end pSeries 690 "Regatta-H" server into 32 partitions. The 36-way Sun Fire 12000 from Sun Microsystems Inc supports only nine dynamic domains, and the top-end 72-way Sun Fire 15000 supports only 18 domains. Hewlett-Packard Co's 64-way Superdome Unix server can support up to 16 dynamic hardware partitions (which HP calls nPars) that can only scale down to a single four-way cell board; HP's vPars virtual partitions are not yet available on the Superdome, but when they will be, they will support single-CPU granularity.

Dynamic AIX LPARs will be available on 16-way pSeries 670 and 32-way pSeries 690 servers next week, according to Mike Harrell, product marketing manager for the pSeries line at IBM. IBM will offer a firmware upgrade on the 4-way pSeries 630 server by the end of the fourth quarter as well, and presumably the forthcoming 4-way and 8-way pSeries 650 will also support the AIX LPARs when they are announced later this year.

In addition to the dynamic partitions, Power4-based pSeries servers running AIX will be able to take advantage of dynamic processor sparing. IBM has offered Capacity Upgrade on Demand (CUoD) configurations in its RS/6000 and pSeries line for years, and this CPU sparing is based on this technology. When customers buy CUoD configurations, they come with a few extra processors so in a pinch customers can quickly and transparently activate those processors. With dynamic processor sparing, if a processor starts to fail or actually fails, AIX 5.2 can take a processor that is earmarked for CUoD and grab it and let it do work while taking the bad CPU offline--hopefully before it causes a system crash. (That is the point, after all.)

Harrell says that the AIX Toolkit for Linux, which is a collection of open source Linux programs that have been compiled to run in AIX, is now up to nearly 400 applications. IBM has also tweaked the Workload Manager within AIX 5.2 to make it possible to better curtail and control Web-based clients accessing applications running on its pSeries servers. AIX 5.2 now also support mobile clients with the IPv6 network protocol, has a journal file system that can support a single file up to 16TB in size (up from 1TB with AIX 5.1).

This bigger JFS2 support is important to customers in the retail, entertainment, and research sectors, where parallel Unix servers are popular and so are very large datasets. (Lawrence Livermore Laboratory, home of the ASCI White supercomputer, needs such a file system, and there are a bunch more in line to get it.

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