The Ext3 File System; Features Of Ext3; Creating An Ext3 File System - Red Hat ENTERPRISE LINUX 4 System Administration Manual

Chapter 6.

The ext3 File System

The default file system is the journaling ext3 file system.

6.1. Features of ext3

The ext3 file system is essentially an enhanced version of the ext2 file system. These improvements
provide the following advantages:
Availability
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.
Data Integrity
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 file system.
Speed
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.
Easy Transition
It is easy to migrate from ext2 to ext3 and gain the benefits of a robust journaling file system
without reformatting. Refer to
perform this task.
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
to an ext3 File System".

6.2. Creating an ext3 File System

After installation, it is sometimes necessary to create a new ext3 file system. For example, if you add a
new disk drive to the system, you may want to partition the drive and use the ext3 file system.
The steps for creating an ext3 file system are as follows:
1. Create the partition using parted or fdisk.
Section 6.3, "Converting to an ext3 File System"
for more on how to
Section 6.3, "Converting
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