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A new server lineup needs a new operating system to match it, and so next month will see the debut of AIX 7.1 from IBM. And about a month earlier than expected, too.

AIX was always the laggard when it came to commercial-grade Unixes, far behind HP-UX from HP and Solaris from Sun Microsystems. And that, along with some pretty pathetic Power-based server iron, meant that HP and Sun controlled the Unix market.

The sad irony these days is that you could make an argument that IBM's Power Systems are the only safe Unix bet when what the IT market really needs is three strong players. Oracle will eventually get its Sparc and x64 server act together, and HP will persevere with Itanium for HP-UX.

There is still room for improvement for IBM's AIX, as there is for every operating system, but the big gut-wrenching changes for AIX were put to bed between AIX 5.1 and 6.1. By comparison, AIX 7.1 is a modest upgrade in functionality that uses the same packaging that IBM has been tweaking with the AIX 6.1 release.

AIX and its companion PowerVM hypervisor, which has been upgraded to the 2.2 release along with AIX 7.1, has logical partitioning as well as workload partitions — IBM's Solarisesque riff on the virtual private server theme — for virtualization. IBM has live partition mobility to move running logical partitions (LPARs, in the IBM lingo) from one physical machine to another, and live application mobility to scoot workload partitions (WPARs, of course) around a pool of networked machines.

PowerVM can scale an LPAR from as small as 1/10th of a processor core (called a micro partition) on a Power System all the way across all 256 cores and 1,024 threads in the full-bore Power 795 machine that was announced this week.

LPARs can be allocated and deallocated dynamically, and PowerVM has features to automatically load-balance LPARs and WPARs as need be in a pool of systems. LPARs can be dedicated to specific resources, or thrown into a shared resource pool where their quality-of-service settings compete for resources.

The LPARs can be hooked into power-management features of the Power Systems iron so processor cores, memory, and other components are shut down as they are not needed, corralling LPARs and WPARs on as few physical components as possible, thereby saving energy. The Power Systems machines have hot-add and hot-remove processor, memory, and I/O with the AIX operating system running, and AIX 6.1-included memory compression as well.

All of these features took the better part of a decade for IBM to add to AIX, and were absolutely necessary for AIX to be a modern operating system. Many of these features were nicked from IBM's proprietary OS/400 operating system, but the Unix people in IBM's Austin, Texas, development lab will never cop to it — just like they'll never really admit that it was the AS/400's Rochester, Minnesota, lab that created the first several generations of the 64-bit Power chips that made it possible for Big Blue to not be an also-ran in the Unix business.

And those wickedly high prices IBM charged for AS/400 and iSeries hardware and software in the late 1990s and early 2000s are precisely what allowed IBM to sell RS/6000 and pSeries hardware at 50 per cent or less of list price and not go broke. IBM screwed one customer base to acquire another — and while that strategy worked as far as quarterly results go, it's kind of stupid when you consider that AS/400 shops were IBM's most loyal customers and about half of its enterprise customer base.

But back to AIX 7.1. Its most important feature is that it is binary compatible with AIX 5.X and 6.1, which means that Power Systems shops do not have to recompile their applications to run them atop AIX 7.1. The latest IBM Unix runs on any machine that uses the dual-core PowerPC 970, Power4, Power4+, Power5, Power5+, Power6, Power6+, or Power7 processors. IBM currently still supports AIX 5.3, which dates from 2005's Power5 generation and which included the Virtual I/O Server and micro-partitioning for AIX for the first time. According to Jeff Howard, director of marketing for IBM's Power Systems division, IBM will continue to support AIX 5.3 until early next year, and indeed, that vintage operating system is supported on current Power7-based machines.

But AIX 5.2 is not, and this is a problem, since it's still out there in pretty large numbers in the RS/6000, pSeries, and System p installed base. So with AIX 7.1, IBM has tweaked its WPAR virtual private servers so they can take a backed up instance of AIX 5.2 and its applications and suck it into a WPAR and run it unchanged.

WPARs use a single, shared AIX kernel and file system across virtual machines instead of logically isolating whole AIX instances inside of partitions to create virtual machines, and this is exactly the kind of thing to which they are well-suited — and moving to new hardware while not changing software is something customers love to do. Howard won't say if a future release of AIX 7 will support AIX 5.3 WPARs, but obviously it will unless IBM has lost its mind.

The AIX 5.2 WPAR support on AIX 7.1 has some limits. IBM's PowerHA clustering cannot span multiple WPARs and cluster them, and IBM's workload-management tools don't work in managing these AIX 5.2 WPAR instances as they did on the real AIX 5.2 machines. For some reason, the NFS file system is also not supported within the AIX 5.2 WPAR; the JFS2 file system is. There are limits to the mobility of the AIX 5.2 WPAR as well.

The AIX 5.2 WPAR feature for AIX 7 carries an additional fee atop of the per-core AIX fees. It costs $60 per core on small Power machines, $170 per core on medium machines, and $310 per core on large machines. If you want the AIX 5.2 WPARs to be mobile, you have to buy PowerVM Workload Partitions Manager for the AIX 7.1 Express or Standard Edition, or get AIX 7.1 Enterprise Edition, which includes this tool as part of its bundle.

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