*=~ShAkE~=*

Get it there ! (v0.30)
Project's page on Savannah
(ebuild is now in the tarball)
Git changelog
(this is GPL-ed software, distributed without any warranty)

What is it ?

Shake is a defragmenter that runs in userspace, without the need of patching the kernel and while the system is used (for now, on GNU/Linux only).
There is nothing magic in that : it just works by rewriting fragmented files. But it has some heuristics that could make it more efficient than other tools, including defrag and, maybe, xfs_fsr.
As an example, it allows you to write find -iname '*.mp3' | sort | shake to defrag all mp3 in a directory, puting together on the disk those close in lexical order.

How to install it ?

If you can, use the package suitable to your distribution. Packages for Ubuntu, Debian, ebuilds and RPM are available on the internet.
If you still want to use the tarball, then install cmake and developpment files for libattr. Then extract the files, open the build/ directory in a terminal, and run cmake .. (to generate the Makefiles), make (to build files) and make install.

How to use it ?

Before any use, check that your partition is mounted with user_xattr. If it is not, edit your fstab to add this option then call mount -o remount MY_PARTITION. Shake can works without them, but will be less efficient (it use xattr to store information helping incremental use).

Short version

As root, call shake my_dir, and go do something usefull or pleasant until it complete. Then my_dir should be less fragmented.
For better results, you should call Shake on the whole partition, when you're not using it.

If you just wanted to see the fragmentation, call shake --pretend --verbose --verbose my_dir, alias shake -pvv my_dir.

Tips

With --old 0 --bigsize 0, you can tell him that all files are old enough, not too big, and so need to be shaked.
If you see a warning saying "failed to set position time", read the above message about setting user_xattr on your partition.

Long version

If you want to adapt the behaviour of Shake, you should read the following lines before.
Shake do the following to decide if a file is fragmented (guilty) or not :

• It first looks at the file size, to determine it's tolerance regarding this file. The less is the tolerance, the more is the probability for a file to be guilty.
  If a file is smaller than small_size (determined with --smallsize, 16 kB by default), then --small-tolerance (0.1 by default) apply.
  If a file is bigger than big_size (determined with --bigsize, 95 mB by default), then by default, the file won't be shaked so you can tell him to let big files quiet. If you want to change this behaviour, set --big-tolerance to something else.
• Then it looks at the date of the last shake (xattr), or the ctime.
  If the file is older than 8*31 days, it will be shaked, in order to reorganise free space. You can change this value with --old
  If a file is newer than 2 month, it won't be shaked. You can change this date with --new.
• If you tell Shake to examine a whole dir, it will look at the distance between two files with the similar atimes (file used together). If this distance is too high, then those files will be shaked.
  The tolerance multiply this distance. You can change the default value with --max-deviance.
• Then, it looks at the actual number of fragments, and class them in two categories.
  The first is the one of crumbs, that is fragments which countains less than crumbratio*file_size bytes. You can change that with --crumbratio.
  The other is the one of all fragments, including crumbs.
  If a file countains more fragments than max_fragc or more crumbs than max_crumbc, then it is considered as guilty.
  You can change max_crumbc and max_fragc respectively with --max-crumbc and --max-fragc.

The code

I will write this section if someone ask for it ^_^.
The fact it runs only on GNU/Linux is due to lack of competence, not to a choice.