An upgrade to IBM's Unix server operating system enhances security and virtualisation capabilities, while providing continuous application availability even during planned downtimes.

AIX 6, announced Thursday, is the first version of AIX to be released in a public beta, a move IBM says demonstrates its desire to win customers away from competitors HP and Sun.

AIX 6 shows IBM is still serious about Unix because it's not a mere "dot release," says Tony Iams, senior analyst in systems software research at Ideas International. While new features related to security and management simply let IBM keep pace with HP and Sun, IBM has broken new ground in the area of virtualisation, says Iams.

IBM says its new Workload Partitions feature is a "software-based virtualisation technology that reduces the number of operating system images that have to be managed when consolidating workloads to increase energy efficiency and reduce costs."

A related upgrade is called Live Application Mobility, which lets users move a workload partition from one server to another even while the workload is running, providing continuous availability similar to a mainframe.

Weakening the bond between workloads, operating systems and hardware is a key goal of virtualisation, Iams notes: "This gives you a very powerful way to migrate workloads from one server to another," he says. "Not just an application but an entire workload, consisting of several applications and middleware."

While AIX 6 won't have quite the same capabilities of a mainframe, Iams says it's notable that IBM is willing to give Unix servers mainframe-like functions even as the company touts the viability of the mainframe.

With previous releases of AIX, IBM offered beta trials to only 30 or 40 existing customers. This time, it is making the beta version freely available on the Web.

IBM expects the final version to come out in November. Pricing will remain the same at US$750 per blade server, including one year of support. Existing customers get a free upgrade to AIX 6.

One security feature IBM touts in its press release - role-based access control - can already be found in HP and Sun products, Iams says. Role-based access control lets businesses define access controls by role, rather than user name. Handy says. That way, database administrators can have one level of access, while system administrators are given a different level of access and end users have still another.

The addition of this feature and several others related to security and management are mostly about catching up to the competition and making sure IBM remains relevant in the Unix market, according to Iams.

Handy boasted about IBM's market share, saying it leads HP and Sun. IDC reported in 2005 that IBM had taken a slim lead over its rivals, though Gartner numbers released at the same time had Sun coming out on top.

Unix systems in general are used for critical workloads. Many users who in the past would have bought mainframes are now considering Unix, Iams says. Though some people have wondered about the relevance of Unix compared to Linux and Windows, Iams notes that Unix offers developers extensive ability to customise. The downside is each Unix system works only on specific hardware platforms.

AIX 6 runs on IBM systems based on Power4, PowerPC 970, Power5 and Power6 processors. Handy says IBM wants to clear up one misconception: AIX 6 is compatible with previous releases, he says, so customers can migrate applications written for AIX 5.3 and 5.2 to the new operating system without extra code work.