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2.6. Storage and File System Improvements

Red Hat Enterprise Linux 6 also features several improvements to storage and file system management. Two of the most notable advances in this version are ext4 and XFS support. For more comprehensive coverage of performance improvements relating to storage and file systems, refer to Chapter 7, File Systems.

Ext4 is the default file system for Red Hat Enterprise Linux 6. It is the fourth generation version of the EXT file system family, supporting a theoretical maximum file system size of 1 exabyte, and single file maximum size of 16TB. Red Hat Enterprise Linux 6 supports a maximum file system size of 16TB, and a single file maximum size of 16TB. Other than a much larger storage capacity, ext4 also includes several new features, such as:

  • Extent-based metadata
  • Delayed allocation
  • Journal check-summing
For more information about the ext4 file system, refer to Section 7.3.1, “The Ext4 File System”.

XFS is a robust and mature 64-bit journaling file system that supports very large files and file systems on a single host. This file system was originally developed by SGI, and has a long history of running on extremely large servers and storage arrays. XFS features include:

  • Delayed allocation
  • Dynamically-allocated inodes
  • B-tree indexing for scalability of free space management
  • Online defragmentation and file system growing
  • Sophisticated metadata read-ahead algorithms
While XFS scales to exabytes, the maximum XFS file system size supported by Red Hat is 100TB. For more information about XFS, refer to Section 7.3.2, “The XFS File System”.
Large Boot Drives

Traditional BIOS supports a maximum disk size of 2.2TB. Red Hat Enterprise Linux 6 systems using BIOS can support disks larger than 2.2TB by using a new disk structure called Global Partition Table (GPT). GPT can only be used for data disks; it cannot be used for boot drives with BIOS; therefore, boot drives can only be a maximum of 2.2TB in size. The BIOS was originally created for the IBM PC; while BIOS has evolved considerably to adapt to modern hardware, Unified Extensible Firmware Interface (UEFI) is designed to support new and emerging hardware.

Red Hat Enterprise Linux 6 also supports UEFI, which can be used to replace BIOS (still supported). Systems with UEFI running Red Hat Enterprise Linux 6 allow the use of GPT and 2.2TB (and larger) partitions for both boot partition and data partition.


Red Hat Enterprise Linux 6 does not support UEFI for 32-bit x86 systems.


Note that the boot configurations of UEFI and BIOS differ significantly from each other. Therefore, the installed system must boot using the same firmware that was used during installation. You cannot install the operating system on a system that uses BIOS and then boot this installation on a system that uses UEFI.
Red Hat Enterprise Linux 6 supports version 2.2 of the UEFI specification. Hardware that supports version 2.3 of the UEFI specification or later should boot and operate with Red Hat Enterprise Linux 6, but the additional functionality defined by these later specifications will not be available.