User`s guide

Parallels Server 4 Bare Metal Basics 15
Virtuozzo File System
Virtuozzo File System (VZFS) is a file system that allows sharing common files among multiple
Containers without sacrificing flexibility. It is possible for Container users to modify, update,
replace, and delete shared files. When a user modifies a shared file, VZFS creates a private copy
of the file transparently for the user. Thus, the modifications do not affect the other users of the
file. Main benefits of VZFS are the following:
 VZFS saves memory required for executables and libraries. A typical Container running a
simple web site might consume around 20–30 MB of RAM just for executable images.
Sharing this memory improves scalability and total system performance.
 VZFS saves disk space. A typical Linux server installation occupies several hundred MB of
disk space. Sharing the files allows you to save up to 90% of disk space.
 VZFS does not require having different physical partitions for different Containers or
creating a special “file system in a file” setup for a Container. This significantly simplifies
disk administration.
 Disk quota enables the administrator to limit disk resources available to a Container on the
fly. Disk quota for users and groups inside Containers is also supported.
Templates
A template (or a package set) in Parallels Server Bare Metal is a set of original application files
repackaged for mounting over Virtuozzo File System. Usually it is just a set of RPM packages
for Red Hat like systems. Parallels Server Bare Metal provides tools for creating templates,
installing, upgrading, adding them to and removing them from a Container. Using templates lets
you:
 share the RAM among similar applications running in different Containers to save hundreds
of megabytes of memory
 share the files comprising a template among different Containers to save gigabytes of disk
space
 deploy applications simultaneously in many Containers
 use different versions of an application on different Containers (for example, perform an
upgrade only in certain Containers)
There are two types of templates: OS templates and application templates. An OS template is an
operating system and the standard set of applications to be found right after the installation.
Parallels Server Bare Metal uses OS templates to create new Containers with a preinstalled
operating system. An application template is a set of repackaged software packages optionally
accompanied with configuration scripts. Application templates are used to add extra software to
existing Containers. For example, you can create a Container on the basis of the redhat OS
template and add the MySQL application to it with the help of the mysql template.
For detailed information on Parallels templates, see the Parallels Server Bare Metal Templates
Management Guide.