Orchestra is one of the most exciting new capabilities in 11.10. It provides automated installation of Ubuntu across sets of machines. Typically, it’s used by people bringing up a cluster or farm of servers, but the way it’s designed makes it very easy to bring up rich services, where there may be a variety of different kinds of nodes that all need to be installed together.
There’s a long history of tools that have been popular at one time or another for automated installation. FAI is the one I knew best before Orchestra came along and I was interested in the rationale for a new tool, and the ways in which it would enhance the experience of people building clusters, clouds and other services at scale. Dustin provided some of that in his introduction to Orchestra, but the short answer is that Orchestra is savvy to the service orchestration model of Juju, which means that the intelligence distilled in Juju charms can easily be harnessed in any deployment that uses Orchestra on bare metal.
What’s particularly cool about THAT is that it unifies the new world of private cloud with the old approach of Linux deployment in a cluster. So, for example, Orchestra can be used to deploy Hadoop across 3,000 servers on bare metal, and that same Juju charm can also deploy Hadoop on AWS or an OpenStack cloud. And soon it should be possible to deploy Hadoop across n physical machines with automatic bursting to your private or favourite public cloud, all automatically built in. Brilliant. Kudos to the conductor 
Private cloud is very exciting – and with Ubuntu 11.10 it’s really easy to set up a small cloud to kick the tires, then scale that up as needed for production. But there are still lots of reasons why you might want to deploy a service onto bare metal, and Orchestra is a neat way to do that while at the same time preparing for a cloud-oriented future, because the work done to codify policies or practices in the physical environment should be useful immediately in the cloud, too.
For 12.04 LTS, where supporting larger-scale deployments will be a key goal, Orchestra becomes a tool that every Ubuntu administrator will find useful. I bet it will be the focus of a lot of discussion at UDS next week, and a lot of work in this cycle.