In the race among No. 1 Unix server seller Sun Microsystems, No. 2 Hewlett-Packard and No. 3 IBM, a key feature has been the ability to split the server into several separate "partitions," a domain with its own operating system and guaranteed access to resources such as memory. The new AIX 5L version 5.2 fulfills an important but as-yet untapped partitioning potential of IBM's Unix servers.
Partitioning lets a computer perform several jobs at once more gracefully, a useful feature when replacing a host of smaller servers with one big one. This "server consolidation" push is one project companies are undertaking, despite the down economy, according to IDC analysts.
But IBM's current Unix servers, unlike Sun's and HP's, haven't been able to tap into one of the most appealing features of partitioning: The ability to expand or contract a partition to adjust to changing workloads. For example, in a retail chain, cash-register transactions might spike at certain times--lunch hours or holiday season sales--while the partition that reconciles accounts in the background might pick up the slack when shops are closed at night.
AIX 5L lets the computer automatically expand or contract partition sizes without rebooting in response to these changing demands, said Karl Freund, vice president of product marketing for IBM's pSeries Unix server line.
This automation is a useful feature for getting more work out of the machine without having to constantly tend to its needs.
The features work on IBM's newer Unix servers, such as the p690 ", its sibling the , and the lower-end .
There are many ways to partition systems, and the top-tier Unix servers are pursuing all of them. Sun, with several years' head start over IBM and HP with Unix server partitioning, prefers physical divisions between partitions that ensure that even major hardware failure in one partition won't affect the other.
IBM, which is newer to Unix server partitioning but has a longer overall track record with the technology in its mainframe line, prefers a software approach. Its "logical" partitions use an extra layer of software between the operating system and the hardware, a layer of abstraction that makes it easier to change the resources allocated to a partition.
HP uses a combination of both approaches.
IBM's approach will get another improvement with AIX 5L version 5.3 coming in 2003, Freund said. Currently, partitions can reside on a single processor, but changes in 5.3 are designed to allow 10 partitions per processor.
This strategy lets administrators run more jobs on a single server.
In the nearer term, AIX 5L 5.2 also comes with an improved "capacity upgrade on demand" feature, which lets a customer buy a server with more processors than initially needed, then pay for the extra processors as computing demands demand.
Version 5.1 allowed new processors to be added in relatively large and expensive eight-processor chunks, but 5.2 will allow them to be added two at a time, a less-expensive increment.
That change effectively reduces the price of another feature, "processor de-allocation," which automatically takes a processor out of the loop if it produces too many errors, then restarts the instructions on a spare processor, Freund said.