Installation guide

Release Notes

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)

4. Storage

4.1. Storage Input/Output Alignment and Size

Recent enhancements to the SCSI and ATA standards allow storage devices to indicate their

preferred (and in some cases, required) I/O alignment and I/O size. This information is particularly

useful with newer disk drives that increase the physical sector size from 512 byes to 4K bytes. This

information may also be beneficial for RAID devices, where the chunk size and stripe size may impact

performance.

The Red Hat Enterprise Linux 6 provides the ability to read and utilize this information, and optimize

how data is read and written from storage devices.

http://docs.redhat.com/docs/en-US/Red_Hat_Enterprise_Linux/6/html/Global_File_System_2/