EXT3 is a journaling version of the EXT2 filesystem discussed in the previous section. It adds a journal to the EXT2 filesystem, which can be done to an existing EXT2 filesystem, enabling easy upgrades. This is not possible with other journaling filesystems because they are not backwards-compatible with EXT2.
EXT3 provides three journaling modes, each of which has different advantages and disadvantages:
■ journal: Logs all filesystem data and metadata changes. The slowest of the three EXT3 journaling modes, this journaling mode minimizes the chance of losing the changes you have made to any file in an EXT3 filesystem.
■ ordered: Logs only changes to filesystem metadata, but flushes file data updates to disk before making changes to associated filesystem metadata. This is the default EXT3 jour-naling mode.
■ writeback: Logs only changes to filesystem metadata but relies on the standard filesystem write process to write file data changes to disk. This is the fastest EXT3 journaling mode.
Beyond its flexibility and the ease with which EXT2 filesystems can be converted to EXT3 filesystems, another advantage of the EXT3 filesystem is that it is also backwards-compatible, meaning that you can mount an EXT3 filesystem as an EXT2 system because the layout on disk is exactly the same. As you will see later in this chapter, this enables you to take advantage of all the existing filesystem repair, tuning, and optimization software that you have always used with EXT2 filesystems should you ever need to repair an EXT3 filesystem.
| r - - r EXT3 is the default on newer versions of openSUSE and is expected to be the default
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