ext3 – journaled file system

ext3, or third extended filesystem, is a journaled file system that is commonly used by the Linux kernel. The journaling capability means no more waiting for fsck’s or worrying about metadata corruption.

It is the default file system for many popular Linux distributions, including Debian. ext3 was originally released in September 1999.

Ext3 partitions contain a used space of 5% for special reasons by default. The main reason is so root can log in even when the filesystem becomes full.

Features include:

  • Simple, robust, and extensible.
  • In-kernel and userspace code has been extensively tested.
  • Adds features to ext2:
    • A journal – improves reliability and eliminates the need to check the file system after an unclean shutdown.
    • Various journal modes: Journal, Ordered, and Writeback.
    • Automatic recover when the filesystem is remounted.
    • All VFS operations (including quota) should be journaled.
    • Add data updates are also journaled.
    • Online file system growth.
    • HTree indexing for larger directories.
  • Extended attribute blocks and large inodes.
  • Online filesystem resize reservations.
  • Hash-indexed directories.
  • Journal file/device present.
  • File type in directory entries.
  • Journal recovery required.
  • Reduced block group backups.
  • Reduced superblock backups.
  • Files larger than 2GiB in size.
  • Easy conversion of ext2 file systems without needing to backup, recover and format the partition.
  • Unix permission, ACLs and arbitrary security attributes.

Website: en.wikipedia.org
Developer: Stephen Tweedie
License: GNU GPL

Return to Journaling File Systems Home Page

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