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MythBusters: Containers Edition
A Contributed Article by James Bottomley, CTO, Server Virtualization, Parallels, Inc.

In the world of virtualized computing, containers have become the hot topic of conversation. Hosting service providers have been using the technology to lower operational costs and increase efficiency for years. But in the enterprise, containers remain a bit of a mystery.

Data centers today are beginning to outgrow the traditional hypervisor method of virtualization. Just as Linux was the upstart operating system that took over the web and found mainstream acceptance, containers are the next wave of web-scale technology to move into the collective awareness of CIOs, CTOs and IT professionals. This is where confusion comes in.

This rogue technology is new to the enterprise, and as a result has perpetuated quite a few myths recently. There are five in particular that we now debunk. 

1.       Containers are not Reliable enough to Support Mission-Critical Workloads

It's hard to understand where this myth comes from. Hosting service providers have been using the technology to lower operational costs and increase efficiency with virtual private servers (VPSs) for over a decade. VPSs are used to provide companies with web and other services like processing credit card transactions. All of which are incredibly mission critical for a business.

2.       Containers are not Secure

While still a myth, this one has a few likely origins. First and foremost, VPS hosting environments were initially largely developed out of the Linux mainstream. Security was not of critical importance in the first Linux containers, so the there's a perception problem with modern containers. In the past three years - Parallels, Google and a host of other companies have been working on pushing all the necessary security technologies upstream. As a result, today's upstream kernel has enough security technology to make containers highly secure and isolated.

The other origin for the containers security myth is based on the granular property of the technology. You can set up a fully-secure, fully-isolated operating system container - but you can also set up a very porous one. There can be good reasons for doing the latter, but it's not always done on purpose. And with most computer systems, security relies on following best practices. These aren't always obvious or followed by people new to containers.

3.       Running Containers inside Virtual Machines adds Efficiency

The belief here is generally that you can overcome the first and second myths by running containers inside virtual machines. While you can do this, you won't actually add efficiency since you lose the density and elasticity of the container system - arguably the two biggest benefits of the technology.

When you run containers in a virtual machine, the final properties are dependent on the hypervisor, which supports less density and is inelastic. Additionally, you add a second layer of virtualization technology, creating more physical and management overhead and three separate technology layers to manage. 

4.       Anything a Container can do, a Hypervisor can Do

In the abstract, this is true because they're both computing environments. But thinking practically, if you give hypervisors and containers similar density and elasticity, you strip down the guest and host of a hypervisor to a point where they become mere shells of themselves. And even after doing this, you still don't have the granular and just-enough virtualization properties of containers. It's a bit like beating a square peg in to a round hole; with a big enough hammer you can do it, but it may not be the best way of achieving the desired outcome.

5.       A Container is a Container

With all of the hype lately about containers, it's not surprising that there's a lot of misinformation being communicated about the technology. Perhaps the best example is how often we hear the phrase: "Docker containers". The truth is - Docker itself is not a container. It is making strides in helping the technology reach a broader audience, but Docker is actually an application packaging and transport system. It relies on the just-enough virtualization properties of containers to function. This confusion often feeds the four myths we referred to above, and can help skew the containers perception problem.

There you have it, five common myths debunked. Now there will always be people willing to compromise on density, elasticity and granularity to ensure that hypervisors are used for specific workloads. However, there are a growing number of use cases that call for mixed environments. And while both technologies have their place, myths aside, containers are making strides to unseat hypervisors as the dominant virtualization technology because they can go places, and do things, that hypervisors just never could. That's the truth.

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About the Author

James Bottomley is CTO of Server Virtualization at Parallels with a current focus on Open Source container technologies and Linux Kernel maintainer of the SCSI subsystem, PA-RISC Linux and the 53c700 set of drivers. He has made contributions in the areas of x86 architecture and SMP, filesystems, storage and memory management and coherency. He is currently a Director on the Board of the Linux Foundation and Chair of its Technical Advisory Board. He was born and grew up in the United Kingdom. He went to university at Cambridge in 1985 for both his undergraduate and doctoral degrees. He joined AT&T Bell labs in 1995 to work on Distributed Lock Manager technology for clustering. In 1997 he moved to the LifeKeeper High Availability project. In 2000 he helped found SteelEye Technology, Inc as Software Architect and later as Vice President and CTO. He joined Novell in 2008 as a Distinguished Engineer at Novell's SUSE Labs and Parallels in 2011.

Published Friday, November 21, 2014 6:40 AM by David Marshall
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