000 applications to manage. Another cause of server sprawl occurs when an application is upgraded. To test the application before it's upgraded, management creates an image of the application, upgrades the image, and then tests the upgrade on a small group of users before making the upgrade available to all users. However, often the original and the upgraded application are left on the physical server, which further contributes to sprawl. To complicate matters further, if either the original or the upgraded version is moved to a different physical server, it can be difficult to determine that there is a duplicate. Containers, which are discussed below, are also vulnerable to sprawl. www.TechnicalPDF.com Containers: A Newer Form of Server Virtualization Containers are servers with a single operating system shared by multiple small programs. Like server virtualization, containers enable a single physical server to hold multiple applications and components of applications. Unlike virtualized servers in which each virtual machine (each application) requires a separate operating system, applications in containers share a single operating system. See Figure 1-10 for a comparison between containers and virtualized servers. This enables containers to hold many more applications than virtualized servers. This is because in virtualized servers, each application has an operating system and also a virtual copy of the hardware that runs the virtual machine. Thus, each operating system uses memory and server capacity. Virtualized server: Each application has its own operating system. Container: Each application (micro service) shares & is compatible with a single operating system. Guest Guest Guest App App2 App3 App 4 www.TechnicalPDF.com Docker engine Hypervisor Host operating system Host operating system Host hardware Host hardware Figure 1-10 A comparison of virtualized servers and containers. In contrast, container technology's use of a single operating system is an efficient use of memory and disk space. Because of this, 