What's in a name? that which we call a zone
By any other name would virtualize as complete;

One of the most common questions raised during boot camps and other Solaris briefings deals with the subject of containers and zones. There seems to be some confusion as the terms appear to be used interchangeably. Yes, they are related - specifically a zone is a new type of container introduced in Solaris 10, but containers have their origins much earlier.

The 1913 Webster dictionary defines a Container as

Container \Con*tain"er\, n.
     1. One who, or that which, contain

which provides the foundation of the Solaris container. Quite simply, a Solaris container is any method by which the resources of an application can be controlled (contained). I suppose the origins of the container could date back to the earliest days of Solaris 2 with the introduction of the processor_bind(2) system call and the pbind(1M) administrative command. These controls were somewhat cumbersome for all but specific workloads and a bit primitive to be called a container.

The container became a recognizable entity with the introduction of the Fair Share Scheduler (FSS) in the Solaris 2.6 timeframe. We had a new scheduler class and a relatively easy to use framework to label and control resource usage for complex applications. So we had a container (project), but it was an unbundled product - so not quite a Solaris container.

When did Solaris get a container ? When the Solaris Resource Manager (SWM) became bundled in Solaris 9. Every instance of Solaris had the capability to control resource usage of nearly every application. Why didn't we call it a container in Solaris 9 ? We only had one type of container (a project), so it wasn't really necessary to give it two different labels. With the introduction of Solaris 10, we have a new type of container, the Solaris zone.

Solaris zones are a virtualization technology that adds a security barrier around each user space instance. We now have two orthogonal application controls: security and resource limits. The name containers was introduced to describe both of these technologies.

So is a zone a container ? Absolutely. As are Solaris Resource Management projects and resource pools. And container technologies can be combined to provide several dimensions of application controls (virtualized user space object, resource caps, resource guarantees). Perhaps there will be other types of containers in the future, but for the moment we have three very interesting technologies that can all wear name container.

Technocrati Tags: Sun Solaris Zones