Earlier this week I’ve read this article: “Defragmentation of Linux Filesystems“. The title and the headline made me interested enough, to go ahead and read it and see if there was something there to show me that linux filesystems do need defragmentation.

when I started using Linux four years later, I was told that with Linux I didn't need to defragment my filesystems anymore, since Linux filesystems don't get fragmented in first place. At that time it left me puzzled, but after a few years of using Linux without defragmenting my filesystems - and without any problems! - it seemed defragmentation was something antique. Nonetheless I still wondered how on earth it was possible the 100k+ files in Gentoo's portage system - updated every time I synchronize the portage tree - didn't fragment my filesystem. Or was my filesystem fragmented and did I not know?

Did you ever hear sentences like “Linux/Unix filesystems are superior, to stuff like NTFS, let alone FAT32 - you don’t even need a defragmentation tool.”?

Mel Gorman posted the seventh version of his Memory Compaction patches asking, "are there any further obstacles to merging?" The patches, first posted in May of 2007, provide a mechanism for moving GFP_MOVABLE pages into a smaller number of pageblocks, reducing externally fragmented memory.

The Filesystem in Userspace (FUSE) project allows you install new filesystems without touching your Linux kernel. The filesystems run as regular programs, allowing them to use shared libraries and perform tasks that would be difficult from inside the Linux kernel. FUSE filesystems look just like regular filesystems to other applications on the machine.

rsnapshot is a filesystem backup utility based on rsync. Using rsnapshot, it is possible to take snapshots of your filesystems at different points in time. Using hard links, rsnapshot creates the illusion of multiple full backups, while only taking up the space of one full backup plus differences. When coupled with ssh, it is possible to take snapshots of remote filesystems as well.

This article covers standard and journaling (also called journaling) filesystems with an emphasis is on ext2 (standard filesystem) and ext3 (journaling filesystem), but tools for other filesystems are mentioned too. Most of this material applies to both 2.4 and 2.6 kernels. Most examples in this article use Fedora 12, with a 2.6.32 kernel. Your results on other systems may differ.

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.

Bonnie++ allows you to benchmark how your filesystems perform various tasks, which makes it a valuable tool when you are making changes to how your RAID is set up, how your filesystems are created, or how your network filesystems perform.