The Ext2 file system is a second-generation Linux extended file system introduced in 1993, while Ext3 is a third-generation file system that was introduced in 2001. Ext3 improves on the Ext2 file system in several ways, most notably with its journaling feature.
Journaling is a file system process that keeps track of every change as it is made. This makes it easier to recover data in the event of a system crash or an unexpected system shutdown. Because the Ext2 lacks the journaling feature of the Ext3 file system, it is considered a less reliable option with hard drives. However, tech experts recommend the use of Ext2 with smaller storage devices such as USB drives.
Under the Ext3, there are three major types of journaling available that affect how data is recorded: ordered, writeback and journal. Ordered refers to the journaling feature where only metadata is stored, after data has been written to the disk. With writeback, metadata may be recorded before or after data has been written. With journal, both the content and metadata are recorded.
Ext2 and Ext3 share several features. Both support a maximum file system size of 32TB and both have hash index directories. Because the two belong in the same family, it is also possible to directly convert an Ext2 file system to Ext3.