Ext4
ext4
ext4 (Fourth Extended Filesystem) is a journaling file system used in the Linux operating system. It is the successor to ext3, offering improved performance, reliability, and support for large storage volumes.
ext4 is the default filesystem for many modern Linux distributions, including Debian, Ubuntu, and Fedora.
Features
- Journaling – Maintains a journal to track changes, improving crash recovery and filesystem integrity.
- Large File and Volume Support – Supports volumes up to 1 exabyte and individual files up to 16 terabytes.
- Extent-based Storage – Uses extents instead of traditional block mapping, reducing fragmentation.
- Delayed Allocation – Allocates space only when data is flushed, optimizing performance.
- Backward Compatibility – Compatible with ext3 and ext2 (can mount them as ext4).
- Persistent Preallocation – Enables applications to preallocate space for files efficiently.
- Faster File System Checks – Due to a redesigned layout, file system checks (fsck) are significantly faster than on ext3.
Usage
ext4 is widely used for general-purpose Linux installations, cloud environments, personal desktops, and servers. It provides a balance of performance, reliability, and simplicity, making it suitable for most workloads.
It is often formatted using:
<syntaxhighlight lang="bash"> mkfs.ext4 /dev/sdX1 </syntaxhighlight>
and checked with:
<syntaxhighlight lang="bash"> fsck.ext4 /dev/sdX1 </syntaxhighlight>
Limitations
While ext4 offers many improvements over ext3, it lacks some features available in more advanced filesystems like Btrfs or ZFS, such as:
- Native snapshots
- Checksumming of data (only metadata is checksummed)
- Built-in RAID or compression features
