Virtualization Management:
Why do IT departments need virtualization management?
Historically, IT administrators provisioned a new server with every new application resulting in a large number of servers with utilization rates of 10-15% or less, commonly known as server sprawl. Server sprawl is responsible for a range of costs.
Why doesn't hardware virtualization solve the issues associated with server sprawl?
Many IT departments have looked to server virtualization management solutions such as VMware and Xen to solve server sprawl. Hardware virtualization consolidates servers and helps to solve the hardware and infrastructure costs, but it can create a new problem "OS or VM sprawl". Any hardware virtualization management technology contains an OS in each virtual machine as well as the host OS (even a "hypervisor" is a Linux-based OS). Also, virtualization management makes provisioning a new OS instance so easy that administrators deploy more detailed and customized OS environments. As a result, administrators must manage hundreds of VM images with many copies of the operating system and IIS, ASP.NET, SQL Server and other middleware that have to be updated independently.
To address this problem Virtuozzo uses a unique template approach to software provisioning that exploits similarities between OS and applications running in different virtual environments. Using templates, administrators can consolidate OS and application management so that only a single instance of a software package is required and managed on a physical machine regardless of the number of virtual environments that use the software.
Virtuozzo templates reduce the duplication of software used multiple times on a virtualized server management, making it possible to manage a single instance of software on a server. A master template is created on the Virtuozzo server in a proprietary template area that is used as a reference for application and OS templates loaded in virtual environments. Instead of physically copying software files and registry entries to each VE, Virtuozzo creates copy-on-write links to the main templates held in the Virtuozzo File System (VZFS) template area. The template provisioned in a VE is the collection of links.
In this illustration, the VEs do not contain copies of the actual bits of the OS and applications; they contain templates with links to the actual OS or application files held on in the VZFS Template Area. A virtual management environment requires an OS template, and may possibly contain one or more application templates.
To keep VEs isolated and to support unique VE configuration requirements, if an OS or application running in a VE writes to a file or a registry entry, the link is broken and changes are made inside the corresponding VE. The dropped link ensures that the master template remains unchanged.
How do other server virtualization technologies treat Operating Systems and applications?
All other commercial server virtualization management use hardware virtualization or para-virtualization. Hardware virtualization has a base-line OS or hypervisor (modified Linux kernel). Each Virtual Machine contains a complete and unique copy of an Operating System and any applications. In the example to the right, the Administrator is now managing four separate OSs and four separate applications. The exact same configuration shown above deployed in Virtuozzo has a single operating system and two applications to manage.
