Novell LINUX ENTERPRISE SERVER 10 - INSTALLATION AND ADMINISTRATION 11-05-2007 Installation Manual page 490

+found). In contrast to journaling file systems, e2fsck analyzes the entire file
system and not 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 desir-
able 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
The code for Ext2 is the strong foundation on which Ext3 could become a highly-
acclaimed next-generation file system. Its reliability and solidity were elegantly
combined with the advantages of a journaling file system.
25.2.3 Ext3
Ext3 was designed by Stephen Tweedie. Unlike all other next-generation file systems,
Ext3 does not follow a completely new design principle. It is based on Ext2. These two
file systems are very closely related to each other. An Ext3 file system can be easily
built on top of an Ext2 file system. The most important difference between Ext2 and
Ext3 is that Ext3 supports journaling. In summary, Ext3 has three major advantages to
offer:
Easy and Highly Reliable Upgrades from Ext2
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 incredibly easy. Unlike transitions
to other journaling file systems, such as ReiserFS or XFS, which can be quite tedious
(making backups of the entire file system and recreating it from scratch), a transition
to Ext3 is a matter of minutes. It is also very safe, because recreating an entire file
system from scratch might not work flawlessly. Considering the number of existing
Ext2 systems that await an upgrade to a journaling file system, you can easily figure
out why Ext3 might be of some importance to many system administrators.
Downgrading from Ext3 to Ext2 is as easy as the upgrade. Just perform a clean
unmount of the Ext3 file system and remount it as an Ext2 file system.
Reliability and Performance
Some other journaling file systems follow the "metadata-only" journaling approach.
This means your metadata is always kept in a consistent state, but the same cannot
be automatically guaranteed for the file system data itself. Ext3 is designed to take
care of both metadata and data. The degree of "care" can be customized. Enabling
472 Installation and Administration