The following ext4 features have been implemented:

  • Metadata checksumming can be enabled by specifying the metadata_csum option when making a file system.

  • 64-bit file system support, which allows you to format a file system that is larger than 16 TB, can be enabled by specifying the 64bit option when making a file system.

  • Improved synchronization speed for database workloads.

  • Improved write-back performance if delayed allocation is disabled using the nodelalloc mount option or if ext2 or ext3 compatibility mode is used.

  • Improved extent-tree memory caching.

  • Improved stabilization of hole punching using fallocate().

  • Improved data and hole seeking using lseek().

The following features are considered experimental and are not supported:

  • Big allocation (bigalloc), which does not currently work with fallocate().

  • Inline data, which stores the data for small files in the available space between on-disk inode data structures.

  • File-system image creation from a directory using mke2fs.

  • Specifying an external journal by using the pathname mount option.