2.5. File System Formats

Read this section for a summary of changes to file system format support between Red Hat Enterprise Linux 6 and Red Hat Enterprise Linux 7.

2.5.1. New Default File System: XFS

XFS is a very high performance, scalable file system and is routinely deployed in the most demanding applications. In Red Hat Enterprise Linux 7, XFS is the default file system and is supported on all architectures.
Ext4, which does not scale to the same size as XFS, is fully supported on all architectures and will continue to see active development and support.
Details of Red Hat support limits for XFS are available at https://access.redhat.com/site/articles/rhel-limits.
For further details about using and administering the XFS file system, see the Red Hat Enterprise Linux 7 Storage Administration Guide, available from http://access.redhat.com/site/documentation/Red_Hat_Enterprise_Linux/.

2.5.1.1. Changes to mount options

Unlike ext3 and ext4, the XFS file system enables the user_xattr and acl mount options by default. This means that you will encounter errors like the following if you include these options at either the command line or in /etc/fstab.
$ mount -o acl /dev/loop0 test
mount: wrong fs type, bad option, bad superblock on /dev/loop0,
       missing codepage or helper program, or other error
      
       In some cases useful info is found in syslog - try
       dmesg | tail or so.
Ext3 and ext4 file systems do not enable these attributes by default, and accept these options when you use the mount command or mount them with /etc/fstab.

2.5.2. Btrfs Technology Preview

Red Hat Enterprise Linux 7 introduces btrfs as a Technology Preview. Btrfs is a next generation Linux file system that offers advanced management, reliability, and scalability features. Btrfs provides checksum verification for files as well as metadata. It also offers snapshot and compression capabilities, and integrated device management.
Details of Red Hat support limits for btrfs are available at https://access.redhat.com/site/articles/rhel-limits. For more information about the level of support available for Technology Preview features, see https://access.redhat.com/site/support/offerings/techpreview/.
For further details about using and administering btrfs, see the Red Hat Enterprise Linux 7 Storage Administration Guide, available from http://access.redhat.com/site/documentation/Red_Hat_Enterprise_Linux/.

2.5.2.1. Kickstarting btrfs

In a kickstart file, to create a partition on the system, you would usually use the part command with the --fstype to create a partition that used a particular file system, like so:
part /mnt/example --fstype=xfs
However, in Red Hat Enterprise Linux 7.0 and 7.1, btrfs is treated more as a device type than a file system type. As such, btrfs is not a valid value for the --fstype parameter. Instead, use the btrfs command to define a btrfs volume, like so:
btrfs mount_point --data=level --metadata=level --label=label partitions

2.5.3. Extended file system support

Red Hat Enterprise Linux 7 introduces a unified extended file system driver that provides support for Ext2, Ext3, and Ext4.
However, Ext2 is considered deprecated as of Red Hat Enterprise Linux 7, and should be avoided if possible.
For further information about these file systems, see the Red Hat Enterprise Linux 7 Storage Administration Guide, available from http://access.redhat.com/site/documentation/Red_Hat_Enterprise_Linux/.