With the release of Red Hat Linux 7.2, Red Hat changed the default file system from the venerable ext2 format to the journaling ext3 file system.
The ext3 file system is essentially an enhanced version of ext2 file system. These improvements provide the following advantages:
After an unexpected power failure or system crash (also called an unclean system shutdown), each mounted ext2 file system on the machine must be checked for consistency by the e2fsck program. This is a time-consuming process that can delay system boot time by a significantly, especially with large volumes containing a large number of files. During this time any data on the volumes is unreachable.
The journaling provided by the ext3 file system means this sort of file system check is no longer necessary after an unclean system shutdown. The only time a consistency check occurs using ext3 is in certain rare hardware failure cases, such as hard drive failures. The time to recover an ext3 file system after an unclean system shutdown does not depend on the size of the file system or the number of files; rather, it depends on the size of the "journal" used to maintain consistency. The default journal size takes about a second to recover, depending on the speed of the hardware.
The ext3 file system provides stronger data integrity in the event that an unclean system shutdown occurs. The ext3 file system allows you to choose the type and level of protection that your data receives. By default, Red Hat Linux 7.3 configures ext3 volumes to keep a high level of data consistency with regard to the state of the file system.
Despite writing some data more than once, ext3 has a higher throughput in most cases than ext2 because ext3's journaling optimizes hard drive head motion. You can choose from three journaling modes to optimize speed, but doing so means trade offs in regards to data integrity.
It is easy to change from ext2 to ext3 and gain the benefits of a robust journaling file system without reformatting. See the Section called Converting to an ext3 File System for more on how to perform this task.
If you perform a fresh installation of Red Hat Linux 7.3, the default file system assigned to the system's Linux partitions is ext3. If you upgrade from a version of Red Hat Linux that uses ext2 partitions, the installation program allows you to convert these partitions to ext3 partitions without losing data. See the appendix titled Upgrading Your Current System in the Official Red Hat Linux Installation Guide for details.
The following sections will walk you through the steps for creating and tuning ext3 partitions. If you have ext2 partitions and are running Red Hat Linux 7.3, you can skip the partitioning and formating sections below and go directly to the Section called Converting to an ext3 File System.