VZFS is an integral part of the virtualization technology developed by Parallels, Inc. It translates to Virtuozzo file system and comprises such product as Parallels Virtuozzo Containers for Linux. VZFS allows to share common files among multiple Containers (Containers) without sacrificing flexibility. This sharing saves up to tens of megabytes of RAM and hundreds of megabytes of disk space for each Container. On the other hand, it remains 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. As an additional advantage, VZFS does not require having different physical partitions for different Containers or creating a special "file system in a file" setup for a Container, which significantly simplifies disk administration.
Virtuozzo Containers 4.0 for Linux comes with a new version of VZFS - Version 2. This paper is destined for Virtuozzo administrators who would like to know more of VZFS v2 and to understand the upgrade path for existing Virtuozzo Containers installations.
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