You may have heard the new buzz word “Cloud Operating System” in the last few months. The term gained prominence when Cloudius Systems launched OSv at LinuxCon in September. Many people working on OSv - namely Glauber Costa, Pekka Enberg, Avi Kivity and Christoph Hellwig - are well known in the Linux community, due to their role in creating KVM. But the concept of a cloud operating system isn’t new. There are many cloud OSes from which to choose, including the Xen Project's Mirage OS, which had its first release a few weeks ago.
Cloud Operating Systems: A New Incarnation of an Older Idea
The approach taken by OSv (as well as others before OSv), revisits an old approach to operating system construction - the Library OS - and puts it in the context of cloud computing within a virtual machine. The basic premise of this approach is to simplify the application stack in the cloud significantly, removing layers of abstraction and offering the promise of less complexity, increased system security and simplified management of application stacks in the cloud.
|Figure 1: on the left, you see a typical application stack run in the cloud today. Of course this is a simplification (leaving out AWS or other cloud APIs). On the right you see. that Cloud Operating systems such as OSv remove the Operating System and replace it with a Language Runtime that is designed to cooperate with the virtual environment the Hypervisor provides (which may include access to Hypervisor APIs).|
As you can see, Cloud Operating Systems are designed to run a single application within a single Virtual Machine: thus much of the functionality in a general purpose operating system is simply removed. In other words, you strip out everything that your language and APIs do not need and let the hypervisor take care of it: what you end up with a lean language specific software stack that runs much faster than a normal VM, and is more secure simply because there is less code that could be attacked.
Examples of Cloud Operating Systems
As stated earlier, OSv is not the first Cloud Operating System on the market. To the credit of OSv’s creators, it did put the technology on the map by creating lots of buzz.