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CHAPTER 4 Preparing for and Testing Docker Containers 37 These materials are © 2017 John Wiley & Sons, Inc. Any dissemination, distribution, or unauthorized use is strictly prohibited. Regardless of how you connect to storage, the often short-lived nature of a container means that latency is an enemy. The longer it takes to instantiate a container or for a container to release its resources once its work is done, the slower the underlying service will operate. Speed is king in the world of containers. Especially today, with the ubiquity and cost-effectiveness of flash media, buying storage that is either all flash or hybrid — a combination of flash and spinning disk — is highly recommended, regardless of application. As Docker continues to mature, expect to see improvements in storage services. More on that topic shortly. Before I move on, though, I want to talk storage capacity. In a virtual machine world, let's assume that you have 100 virtual machines, each with a 10GB virtual disk for the OS. That equates to a terabyte of storage used just for the OS. In the container environment, you have a single OS instance, so that takes up 10GB. Each container in then just a fraction of the size of a virtual machine and could be just a few megabytes. You can quickly gain capacity savings by moving to containers. In fact, in a study carried out jointly by Docker and HPE, containers saw a greater than 30% savings in storage capacity when compared to certain virtual machine configurations.