The Linux 3.1 kernel isn't making it out for a few more weeks and just before the final release, so Canonical is playing it safe and sticking to the Linux 3.0 kernel although the still-in-development release does provide some nice improvements to the DRM graphics drivers and other areas of the kernel. Users can manually upgrade to the Linux 3.1 kernel and it should be relatively safe.
Over Mesa 7.10.2, which shipped in Ubuntu 11.04, the Mesa 7.11 release has many improvements. See the linked article for full details, but there's support for new OpenGL extensions, there's slowly more of OpenGL 3.0, more mature Intel Sandy Bridge support, initial Intel Ivy Bridge support, new AMD hardware support, GLSL compiler improvements, Gallium3D enhancements, better Nouveau driver support, and many bug-fixes. Ubuntu is not shipping Mesa with floating-point textures for obvious legal concerns.
The xorg-server package in Ubuntu Oneiric has not received a major upgrade. X.Org Server 1.10 was also the release used in Ubuntu 11.04. There is now X.Org Server 1.11 that carries a lot of bug-fixes, and not much in the way of introducing major features, but it was decided early by Canonical they did not want to follow xorg-server 1.11. The 1.11 release does not merge some of the input work they have been tackling and they wanted to play it safer in case AMD (or NVIDIA) was slow again in supporting the ABI used by the new xorg-server release.
If you're building an internal or private cloud, Canonical wants you to use Ubuntu Linux 10.04 as your operating system of choice. To that end, the newest version of Ubuntu includes a feature set called Ubuntu Enterprise Cloud.
Getting startedIn order to successfully run Ubuntu Enterprise Cloud, we had to have at least two dedicated systems. One is used for the front-end applications, which include a Cloud Controller, a Cluster Controller, Walrus Controller, and the Storage Controller. The other system became a node machine that ran the hosted virtual machines.
The controller services were easy to understand since they're similar to Amazon EC2 Cloud components. The Ubuntu Enterprise Cloud Cloud Controller is the front-end service application — the one to connect to for managing cloud services. It understands EC2 API calls, and offered us its Web user interface.
The Cluster Controller, in turn, manages each cluster of node (VM) resources, and talks to the node/VM host via the open source libvrt library. We could use as many nodes as we had hardware resources to cram them into; Canonical recommends baseline hardware and recommends faster components, even down to disk speed.