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3. File Systems


The Storage Administration Guide provides further instructions on how to effectively manage file systems on Red Hat Enterprise Linux 6. Additionally, the Global File System 2 document details specific information on configuring and maintaining Red Hat Global File System 2 for Red Hat Enterprise Linux 6.

3.1. Fourth Extended Filesystem (ext4) Support

The fourth extended filesystem (ext4) is based on the third extended filesystem (ext3) and features a number of improvements. These include support for larger file systems and larger files, faster and more efficient allocation of disk space, no limit on the number of subdirectories within a directory, faster file system checking, and more robust journaling. The ext4 file system is selected by default and is highly recommended.

3.2. XFS

XFS is a highly scalable, high-performance file system which was originally designed at Silicon Graphics, Inc. It was created to support filesystems 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. The XFS file systems can also be defragmented and expanded while mounted and active.

3.3. Block Discard — enhanced support for thinly provisioned LUNs and SSD devices

Filesystems in Red Hat Enterprise Linux 6 use the new block discard feature to allows a storage device to be informed when the filesystem detects that portions of a device (also known as blocks) are no longer in active use. While few storage devices feature block discard capabilities, newer solid state drives (SSDs) utilize this feature to optimize internal data layout and invoke proactive wear levelling. Additionally, some high end SCSI devices use block discard information to help implement thinly provisioned LUNs.

3.4. Network File System (NFS)

A Network File System (NFS) allows remote hosts to mount file systems over a network and interact with those file systems as though they were mounted locally. This enables system administrators to consolidate resources onto centralized servers on the network. Red Hat Enterprise Linux 6 supports NFSv2, NFSv3, and NFSv4 clients. Mounting a file system via NFS now defaults to NFSv4.
Additional improvements have been made to the NFS in Red Hat Enterprise Linux 6, providing enhanced support over Internet Protocol version 6 (IPv6)