"The first supported file system for Linux was the Minix file
system. This file system had some significant performance issues,
so another file system was created specifically for Linux called
the extended file system. The first extended file system (ext1) was
designed by Remy Card and introduced into Linux in April 1992. The
ext1 file system was the first to use the virtual file system (VFS)
switch implemented in the 0.96c kernel and supported file systems
up to 2 gigabytes (GB) in size.
"The second extended file system (ext2), also implemented by
Remy Card, was introduced in January 1993. It adopted advanced
ideas from other file systems of the day (such as the Berkeley Fast
File System [FFS]). Ext2 extended supported file systems of 2TB in
size, although 2.6 kernels extended the maximum size of ext2 file
systems to 32TB.
"The third extended file system (ext3) was a major advance in
Linux file systems, even though its performance was less than some
of its competitors. The ext3 file system introduced the concept of
journaling to improve the reliability of the file system when the
system is abruptly halted. And although competing file systems had
better performance (such as Silicon Graphics' XFS and the IBM®
Journaled File System [JFS]), ext3 supported in-place upgrades from
systems already using ext2. Ext3 was introduced in November 2001
and implemented by Stephen Tweedie.
"Fast-forward to today. We now have the fourth extended file
system (ext4). Ext4 introduces numerous new advancements for
performance, scalability, and reliability. Most notably, ext4
supports file systems of 1 exabyte in size. Ext4 was implemented by
a team of developers, led by Theodore Tso (the ext3 maintainer),
and was introduced in the 2.6.19 kernel. It is now stable in the
2.6.28 kernel (as of December 2008).
"Ext4 borrows many useful concepts from a variety of competing
file systems. For example, the extent approach to block management
had been implemented in JFS. Another block management-related
feature (delayed allocation) was implemented in both XFS and in Sun
Microsystems' ZFS.
"You'll find various improvements and innovations in the new
ext4 file system. The improvements cover a number of feature angles
from new functionality (new features), scalability (scaling beyond
current file system constraints), reliability (in the face of
failures), and of course, performance."
