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Chapter 5. File Systems

Support of Btrfs File System

The Btrfs (B-Tree) file system is supported as a Technology Preview in Red Hat Enterprise Linux 7.1. This file system offers advanced management, reliability, and scalability features. It enables users to create snapshots, it enables compression and integrated device management.


The OverlayFS file system service allows the user to "overlay" one file system on top of another. Changes are recorded in the upper file system, while the lower file system remains unmodified. This can be useful because it allows multiple users to share a file-system image, for example containers, or when the base image is on read-only media, for example a DVD-ROM.
In Red Hat Enterprise Linux 7.1, OverlayFS is supported as a Technology Preview. There are currently two restrictions:
  • It is recommended to use ext4 as the lower file system; the use of xfs and gfs2 file systems is not supported.
  • SELinux is not supported, and to use OverlayFS, it is required to disable enforcing mode.

Support of Parallel NFS

Parallel NFS (pNFS) is a part of the NFS v4.1 standard that allows clients to access storage devices directly and in parallel. The pNFS architecture can improve the scalability and performance of NFS servers for several common workloads.
pNFS defines three different storage protocols or layouts: files, objects, and blocks. The client supports the files layout, and since Red Hat Enterprise Linux 7.1, the blocks and object layouts are fully supported.
Red Hat continues to work with partners and open source projects to qualify new pNFS layout types and to provide full support for more layout types in the future.
For more information on pNFS, refer to