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?

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.

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.

Ext4 is the latest in a long line of Linux® file systems, and it's likely to be as important and popular as its predecessors. As a Linux system administrator, you should be aware of the advantages, disadvantages, and basic steps for migrating to ext4.

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.

Last night I managed to finish up a rather satisfying improvement to ext4’s inode and block allocators. The ext4’s original allocator was actually a bit more simple-minded than ext3’s, in that it didn’t implement the Orlov algorithm to spread out top-level directories for better filesystem aging.

Over the past week there has been a lot of talk about the EXT4 file-system following the announcement that Google is migrating their EXT2 file-systems to EXT4. Their reasons for this transition to EXT4 are attributed to the easy migration process and Google engineers are pleased with this file-system's performance.

Most often, when someone talks about a filesystem or file system, they're referring to disk filesystems such as NTFS, FAT, ext2, ext3, ext4, ISO 9660 and many others but can also refer to network file systems such as CIFS (Common Internet File System aka Samba) and NFS. A filesystem is a specially-designed database of files, their disk location, definition and attributes.