Ext2 - Novell LINUX ENTERPRISE SERVER 11 - STORAGE ADMINISTRATION GUIDE 2-23-2010 Administration Manual

The terms data integrity and data consistency, when used in this section, do not refer to the
consistency of the user space data (the data your application writes to its files). Whether this data is
consistent must be controlled by the application itself.
IMPORTANT: Unless stated otherwise in this section, all the steps required to set up or change
partitions and file systems can be performed by using YaST.
Section 1.2.1, "Ext2," on page 14
Section 1.2.2, "Ext3," on page 15
Section 1.2.3, "Oracle Cluster File System 2," on page 16
Section 1.2.4, "ReiserFS," on page 16
Section 1.2.5, "XFS," on page 17

1.2.1 Ext2

The origins of Ext2 go back to the early days of Linux history. Its predecessor, the Extended File
System, was implemented in April 1992 and integrated in Linux 0.96c. The Extended File System
underwent a number of modifications and, as Ext2, became the most popular Linux file system for
years. With the creation of journaling file systems and their short recovery times, Ext2 became less
important.
A brief summary of Ext2's strengths might help understand why it was—and in some areas still is—
the favorite Linux file system of many Linux users.
"Solidity and Speed" on page 14
"Easy Upgradability" on page 14
Solidity and Speed
Being quite an "old-timer," Ext2 underwent many improvements and was heavily tested. This might
be the reason why people often refer to it as rock-solid. After a system outage when the file system
could not be cleanly unmounted, e2fsck starts to analyze the file system data. Metadata is brought
into a consistent state and pending files or data blocks are written to a designated directory (called
lost+found
just the recently modified bits of metadata. This takes significantly longer than checking the log data
of a journaling file system. Depending on file system size, this procedure can take half an hour or
more. Therefore, it is not desirable to choose Ext2 for any server that needs high availability.
However, because Ext2 does not maintain a journal and uses significantly less memory, it is
sometimes faster than other file systems.
Easy Upgradability
Because Ext3 is based on the Ext2 code and shares its on-disk format as well as its metadata format,
upgrades from Ext2 to Ext3 are very easy.
14 SLES 11: Storage Administration Guide
). In contrast to journaling file systems, e2fsck analyzes the entire file system and not