ext3 and ext4 file systems can be converted to btrfs. For non-root file systems, this can be done online (i.e., without reboot), while for root file systems we need to boot into some kind of rescue system or Live CD. This guide explains how to convert an ext3 or ext4 root file system into btrfs on Ubuntu 12.10 and how to roll back to ext3/ext4 again if desired.

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.

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.

To see how this changes the Linux file-system landscape, atop the latest Linux kernel we have a fresh set of benchmarks for EXT3, EXT4, XFS, ReiserFS, and Btrfs.

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.

One might think that the ext3 filesystem, by virtue of being standard on almost all installed Linux systems for some years now, would be reasonably well tuned for performance. Recent events have shown, though, that some performance problems remain in ext3, especially in places where the fsync() system call is used.

There is no shortage of EXT4 benchmarks from comparing this evolutionary file-system's performance on netbooks to how it battles the Btrfs file-system to its performance recession. In this article though we are finally delivering something that has long been requested and that is Reiser4 file-system benchmarks running directly against EXT4 and Btrfs.

A number of senior kernel developers, including Linus Torvalds, Ted Ts'o, Alan Cox and Ingo Molnar, have been squabbling over the sense or otherwise of journaling and delayed allocation in Ext3 and Ext4.

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.