Sun is delivering on its promise, made last October, to roll out a new form of virtualisation, which it is calling logical domains or LDoms.

According to Sun, logical domains are a different approach to virtualisation than Solaris Containers, which are OS-level virtual machines and were introduced along with Solaris 10. Instead, Sun blogger Tony Kay described them as "a hypervisor-based technology on Sun's CMT platforms, today the T1000 and T2000 platforms.

"Architecturally there are some fundamental similarities between LDoms and x86-based hypervisors such as VMware's ESX and Xen," he said.

The partitions are handled directly by Sun's T1 UltraSparc (Niagara) CPUs through the Sun4V hypervisor, with a current limitation to maximum 32 fully isolated domains (on eight-core CPUs). In other words, they're closer in concept to VMware's hardware-level virtualisation system, which centres around the ESX Server hypervisor.

According to Sun's white paper, Beginners Guide to LDoms: Understanding and Deploying Logical Domains, the technology offers benefits similar to other hardware-level virtualisation systems. It allows users "to allocate a system’s various resources, such as memory, CPUs, and devices, into logical groupings and create multiple, discrete systems, each with their own operating system, resources, and identity within a single computer system."

The white paper said that "a logical domains environment can help achieve greater resource usage, better scaling, and increased security and isolation."

Sun sees LDoms fitting between OS-level virtualisation and its dynamic system domains, where virtual machines are electrically isolated by the Sparc CPU.

It's unclear whether you'll only be able to run Solaris, or whether Sun will allow other OSes to be run. To do so, however, it would probably need to develop CPU emulation technology, which it's shown no signs of doing.

The software is currently in release candidate 3 state and is available for download free. But although the company said it will release the technology free, customers will have to pay for a support contract.