Container Patterns

Containers can be deployed in several ways, depending on goals and usage scenarios. Let's have a look at typical patterns and view this in light of z Systems:

Docker and z/VM or KVM?

At LinuxCon, KVM for z has been announced. From a Docker perspective, what does KVM change over a z/VM environment? There's a pretty short answer: nothing. KVM is cool for a number of things, z/VM is still king of the road, PR/SM still has got some bragging rights, and Docker doesn't care, as long as a Linux runs in it. Docker under both z/VM and KVM benefits from complementing technologies.

Virtualization vs. Containerization

Containers provide isolated runtime environments for applications: the entire user space environment is exclusively presented to the container, and any changes to it do not impact other containers' environments. To provide this isolation, a combination of OS-based mechanisms is used: Linux name spaces are used for isolation and scoping mechanism. File system mounts define what files are accessible to the container. cgroups define resource consumption of containers. Still all containers share the same OS kernel which can realize memory footprint efficiencies when identical libraries are used by multiple containers.

With system virtualization, the hypervisor provides a full virtual machine to a guest: the entire OS image including the kernel is now dedicated to the virtual machine. CPU virtualization is used to provide each guest with an exclusive view of a full system environment, and these mechanisms also ensure isolation from other guests. Hypervisor-based management of virtual CPUs, memory and I/O devices is used to define resource consumption of guests.

Which one is better?