The ext3 filesystem uses the same on-disk format as ext2, but adds journaling capabilities. In fact, of all the Linux filesystems, ext3 has the most extensive journaling support, supporting not only metadata journaling but also ordered journaling (the default) and full metadata+data journaling. These "special" journaling modes help to ensure data integrity, not just short fscks like other journaling implementations. For this reason, ext3 is the best filesystem to use if data integrity is an absolute first priority. However, these data integrity features do impact performance somewhat. In addition, because ext3 uses the same on-disk format as ext2, it still suffers from the same scalability limitations as its non-journalled cousin. Ext3 is a good choice if you're looking for a good general-purpose journalled filesystem that is also very robust.

• In kernels: 2.4.16+
• journaling: metadata, ordered data writes, full metadata+data
• mkfs command: mke2fs -j
• mkfs example: mke2fs -j /dev/hdc7
• related commands: debugfs, tune2fs, chattr
• performance-related mount options: noatime, nodiratime
• other mount options:
  • data=writeback (disable journaling)
  • data=ordered (the default, metadata journaling and data is written out to disk with metadata)
  • data=journal (full data journaling for data and metadata integrity. Halves write performance.)
• ext3 resources:
  • Andrew Morton's ext3 page
  • Andrew Morton's excellent ext3 usage documentation (recommended)
  • Advanced filesystem implementor's guide, part 7: Introducing ext3
  • Advanced filesystem implementor's guide, part 8: Surprises in ext3