The ext3 file system is essentially an enhanced version of the 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 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 that 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, the ext3 volumes are configured to keep
a high level of data consistency with regard to the state of the
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.
The following sections walk you through the steps for creating and
tuning ext3 partitions. For ext2 partitions, skip the partitioning and
formating sections below and go directly to Section 6.3 Converting to an ext3 File System.