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 OS installation occupies several hundred megabytes 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.