Infrastructure-as-a-Service compute clouds provide a flexible hardware platform on which customers host applications as a set of appliances, e.g., web servers or databases. Each appliance is a VM image containing an OS kernel and userspace processes, within which applications access resources via traditional APIs such as POSIX. However, the flexibility provided by the hypervisor comes at a cost: the addition of another layer in the already complex software stack which impacts runtime performance, and increases the size of the trusted computing base.

Given that modern software is generally written in high-level languages that abstract the underlying OS, we revisit how these appliances are constructed with our Mirage operating system. Mirage supports the progressive specialisation of source code, and gradually replaces traditional OS components with customisable libraries, ultimately resulting in "unikernel" VMs: sealed, fixed-purpose VMs that run directly on the hypervisor.

Developers no longer need to become sysadmins, expert in the configuration of all manner of system components, to use cloud resources. At the same time, they can develop their code using their usual tools, only making the final push to the cloud once they are satisfied their code works. As they explicitly link in components that would normally be provided by the host OS, the resulting unikernels are also highly compact: facilities that are not used are simply not included in the resulting microkernel binary.

This talk will describe the architecture of Mirage, and show a quick demonstration of how to build a web-server that runs as a unikernel on a standard Xen installation.

Rackspace has years of experience with running Xen at scale, starting with Xen and migrating to XenServer. We will share why we use Xen/XenServer along with some of the issues that we've experienced. We will touch on our experience with migrating from Xen to XenServer and the challenges there. We will share information about Rackspace Cloud Servers architecture, and touch briefly on OpenStack when doing so. We will explain how we use Xen to quickly deploy new Openstack services with what we call Nova on Nova. And finally, we will discuss what additional features and improvements are needed and why.

In a traditional Xen configuration domain 0 is used for a large number of different functions including running the toolstack(s), backends for network and disk I/O, running the QEMU device model instances, driving the physical devices in the system, handling guest console/framebuffer I/O and miscellaneous monitoring and management functions. Having all these functions in one domain produces a complex environment which is susceptible to shared fate on the failure of any one function, has complex interactions between functions (including resource contention) which makes it difficult to predict performance, and has limited flexibility (such as requiring the same kernel for all device drivers).

""Domain 0 disaggregation"" has been discussed for some time as a way to break out domain 0's functions into separate domains. Doing this enables each domain to be tailored to its function such as using a different kernel or operating system to drive different physical devices. Splitting functions into separate domains removes some of the unintentional interactions such as in-domain resource contention and reduces the system impact of the failure of a single function such as a device driver crash.

Although domain 0 disaggregation is not new it is seldom used in practise and much of its use is focussed on providing enhanced security. Citrix XenServer will be moving towards a disaggregated domain 0 in order to provide better security, scalability, performance, reliability, supportability and flexibility. This talk will describe XenServer's “Windsor” architecture and explain how it will provide the above benefits to customers and users. We will present an overview of the architecture and some early experimental measurements showing the benefits.

CloudStack, the world's leading open-source cloud infrastructure platform, was recently donated to the Apache Foundation, and is now an incubated Apache project. Ewan Mellor, Director of Engineering in the Citrix Cloud Platforms Group will describe the CloudStack project and explain why Xen is the pre-eminent hypervisor in public clouds today. He will describe the changes coming in CloudStack in the next 12 months, and how they are going to change the way that Xen is consumed in public and private clouds next year.

Cloud leaders such as Rackspace and Internap are building their next generation cloud using OpenStack and Xen+XenAPI, not everyone uses OpenStack with KVM. Lets take a look at how OpenStack and Xen work together, and look at how you can get more involved.