Chapter 4. File Systems

Support of XFS File System

The default file system for an Anaconda-based installation of Red Hat Enterprise Linux 7 is now XFS, which replaces the Fourth Extended Filesystem (ext4) used by default in Red Hat Enterprise Linux 6. The ext4, ext3 and ext2 file systems can be used as alternatives to XFS.
XFS is a highly scalable, high-performance file system which was originally designed at Silicon Graphics, Inc. It was created to support file systems up to 16 exabytes (approximately 16 million terabytes), files up to 8 exabytes (approximately 8 million terabytes) and directory structures containing tens of millions of entries. XFS supports metadata journaling, which facilitates quicker crash recovery. XFS file system can also be defragmented and expanded while mounted and active. Note that it is not possible to shrink XFS file system.
For information about changes between commands used for common tasks in ext4 and XFS, see the Reference Table in the Installation Guide.

Support of Btrfs File System

The Btrfs (B-Tree) file system is supported as a Technology Preview in Red Hat Enterprise Linux 7. This file system offers advanced management, reliability, and scalability features. It enables users to create snapshots, it allows for compression and integrated device management.
For more information about the Btrfs Technology Preview, see Storage Administration Guide

Fast Block Devices Caching Slower Block Devices

LVM provides the ability to have fast block devices act as a cache for slower block devices. This feature is introduced as a Technology Preview in Red Hat Enterprise Linux 7 and allows a PCIe SSD device to act as a cache for direct-attached storage (DAS) or storage area network (SAN) storage, which improves file system performance.
For more information, refer to the LVM Cache entry in Chapter 3, Storage and the lvm(8) manual page.