I did mention that the new filesystem - ext4 is stable, fast and backward compatible with ext2 and ext3. Today, we will look at how you can upgrade your existing ext3 filesystem to ext4 without reformating your hard disk.

The filesystem used in the vast majority of Linux (and to a lesser extent on other Unix) distributions is the ext3 filesystem, which stands for extended filesystem. Slashdot recently pointed to an article on IBM DeveloperWorks discussing the new ext4 filesystem currently in development, and some of its new features. So what is a filesystem really?

This article is meant to serve as a guide for migrating a live system from ext3 to an ext4 filesystem, including migration of files to use extents, a major feature in ext4.

You can convert your existing Ext3 filesystem to Ext4 with an easy procedure.Things to remember
* Unmount the filesystem before convert
* Filesystem must be non-root
This way you can improve the performance, storage limits and features of your existing filesystem without reformatting and/or reinstalling your OS and softwares.

Over the weekend, I converted my laptop to use the ext4 filesystem. So far so good! So far I’ve found one bug as a result of my using ext4 in production (if delayed allocation is enabled, i_blocks doesn’t get updated until the block allocation takes place, so files can appear to have 0k blocksize right after they are created, which is confusing/unfortunate), but nothing super serious yet.

This is somewhat of a simple observation on my part, but one of the things I've noticed of late is how the cry for Ext4 is growing, and fast. Sure, recent benchmarks make it look like the ultimate solution. But I don't recommend moving to the Ext4 file system just yet.

It all started back in the good ol’ days of the Jaunty development cycle when I heard this new fangled filesystem thingy called ext4 was going to be an option in Jaunty. It claimed to be faster with much shorter fsck times. So, like any good Ubuntu developer, I tried it.

With the EXT4 file-system having been stabilized with the Linux 2.6.28 kernel, the Ubuntu developers are preparing to adopt this evolutionary Linux file-system update. EXT4 will not replace EXT3 as the default file-system until at least Ubuntu 9.10, but as of yesterday, Ubuntu 9.04 now has install-time support for EXT4.

There's been a certain amount of discussion about behavioural differences between ext3 and ext4[1], most notably due to ext4's increased window of opportunity for files to end up empty due to both a longer commit window and delayed allocation of blocks in order to obtain a more pleasing on-disk layout.