Overview
UNIX
64-bit
Networking
Open Directory
File system
Security controls
Xgrid
Apple’s Xgrid technology makes it easy to turn an ad hoc group of Mac systems into a low-cost supercomputer. Leveraging the power of Mac OS X Server, Xgrid is an ideal distributed computing platform for individual researchers, specialised collaborators and application developers.
Power in numbers.
Take any number of portable computers, desktops and servers and turn them into a single computational cluster — in a matter of minutes. Xgrid technology leverages the power of Mac OS X Server’s UNIX foundation, zero-configuration Bonjour technology and directory services architecture to streamline configuration — while administration tools make it easy to manage Xgrid clusters, submit jobs, monitor progress and retrieve results.
Configuration in an instant.
Since Xgrid is built into Mac OS X and Mac OS X Server, configuration is easy. Using Xgrid Admin (or the command line, if you prefer), just designate one system as controller, then enable additional systems to act as Xgrid agents. All agents use the zero-configuration Bonjour technology to find the controller and bind to it automatically — no need to manually enter a slew of IP addresses.
Distributed computing — anywhere and everywhere.
The power of Xgrid doesn’t end at the nearest router. Using the DNS service lookup in Bonjour, agents can query your organization’s nameserver to find the appropriate controller, no matter where it is. In fact, you can set up a controller that’s accessible from the public Internet and any Xgrid-capable system can join the grid just by using your host name or IP address. That means Xgrid clusters can range from a single rack of Xserve systems to a roomful of Mac Pro computers to a diverse collection of Mac systems dispersed across the Internet.
Support for shared file systems. 
Snow Leopard Server now works with server clusters on a shared file system such as Xsan or NFS. So important data in the cluster is always available to every server on the network — no need to copy data from one place to another.
Scalability and high availability.
The Xgrid controller is designed to scale as your projects grow more complex. In fact, it works as hard as the hardware you’re running. Since Xgrid handles jobs that crunch for days, if not months, it needs to deal gracefully with disruptions. Xgrid automatically detects when an agent is no longer accessible and reassigns the task to another system. Essential job information is cached on disk, so your grid can resume work immediately if you should ever need to reboot the controller.
The right Mac for the job.
The Scoreboard feature in Xgrid brings tremendous intelligence to the distribution of tasks, making the most of available processing power. Much more than a batch-processing system, Scoreboard prioritises jobs and sends them to Xgrid nodes with the required features or capabilities. Since each node reports its configuration to the controller, Scoreboard knows which available agents — for example — have a 64-bit Intel processor with more than 4GB of RAM and are connected to an Xsan network. In this way, Scoreboard makes sure that jobs are sent first to those agents that can handle the work most efficiently.
Cluster management.
The Xgrid Admin application, included with Mac OS X Server, gives you an overview of all the agents, jobs and tasks that your servers are managing. As administrator, you can stop, pause, resume, or delete jobs — or partition available agents into separate clusters, which allows different groups to share a single controller without interfering with each other. And you can bring up a tachometer to revel in how many gigahertz are turning over inside your supercomputer.
