1 About File System Management

This chapter describes local file system management in Oracle Linux. Information about file systems and minimum requirements for each file system type is also provided.

Supported File Systems

Oracle Linux supports many local file system types that you can configure on block devices, which include the following:

btrfs

A copy-on-write file system that's designed to address the expanding scalability requirements of large storage subsystems. Btrfs supports the following: snapshots, a roll-back capability, checksum functionality for data integrity, transparent compression, and integrated logical volume management.

Note:

In Oracle Linux 8, the Btrfs file system type is supported on Unbreakable Enterprise Kernel (UEK) releases only.

ext4

A version of the extended file system. Ext4 supports the same features that are supported by Ext3, with added support for extents or contiguous physical blocks, preallocation, delayed allocation, speedier file system checking, more robust journaling, and several other enhancements.

XFS

A high-performance, journaling file system that provides high scalability for I/O threads, file system bandwidth, file size, and file system size, even for file systems that span many storage devices.

To list recognized file system types on a system, use the following command:

sudo ls /sbin/mkfs.*

Note that the following output might differ, depending on the setup:

sudo ls /sbin/mkfs.*
/sbin/mkfs.cramfs   /sbin/mkfs.ext4   /sbin/mkfs.msdos
/sbin/mkfs.ext2     /sbin/mkfs.fat    /sbin/mkfs.vfat
/sbin/mkfs.ext3     /sbin/mkfs.minix  /sbin/mkfs.xfs

These executables are used to make the file system type that's specified by their extension. For example, mkfs.msdos is the other name for mkdosfs. The mkfs.cramfs command creates a compressed ROM, read-only cramfs file system for use by embedded or small-footprint systems.

Maximum File and File System Size Requirements

File system limitations are affected by kernel versions and features, and also by the architecture of the system on which Oracle Linux is installed. The values that are shown in the table are estimates, based on the known variables that might affect the maximum theoretical value that can be achieved. The theoretical values might be greater than those depicted here, while the actual, achievable values might be lesser than the values that are shown, depending on the hardware and kernel version that's used.

The following table describes the maximum file size and maximum file system size for the btrfs, ext4, and xfs file systems.

File System Type	Maximum File Size	Maximum File System Size	Supported Kernels
btrfs	8 EiB	8 EiB	UEK, starting with Unbreakable Enterprise Kernel Release 6 (UEK R6)
ext4	16 TiB	1 EiB	RHCK and UEK
xfs	8 EiB	8 EiB	RHCK and UEK

The limits for the ext4 file system that are described in the previous table are greater than those recommended and might prove unstable. If you intend for the systems you work on to eventually use bigger file system sizes or file sizes, then using either the Btrfs or XFS file system is recommended.

The maximum supported size for a bootable logical unit number (LUN) is 50 TB. GPT and UEFI support are required for LUNs that are larger than 2 TB.

The maximum size of the address space that's available to each process is 128 TB.

For information about maximum file sizes and maximum file system sizes for OCFS2, see the chapter on OCFS2 in Oracle Linux 8: Managing Shared File Systems.