File system fragmentation

[Douglas Furlong]

On Fri, 2004-10-08 at 09:08 -0400, Mark Haney wrote:
> What's the story with ext3 file fragmentation?  Are there any gain in
> defragmenting the file system?  Does ext3 suffer from file
> fragmentation?  I'm sure this has been discussed before, but I want
> real-world opinions, not just suppositions.
> 
> The reason I ask is the performance of Evolution on my machine is
> deteriorating as I accumulate more email.  I'm sure some of this is just
> due to the size of my Inbox (170MB or so) and Evolution's handling of
> it, but would a defragmenter help this at all?
>From what I can tell of previous conversations, the fragmentation is
heavily dependant on free disk space.

The less space available to the kernel when storing data, the higher the
level of fragmentation.

Any easy, but troublesome way of defragmenting a particular low system,
is to copy the data from one partition/disk to another. Then copy it
back again (assuming that your free space is sufficient to allow the
system to cope with fragmentation).

I believe EXT3 starts to have a performance hit around 60% to 70% of
capacity and on, problems becoming more and more acute the less space
available.

You can use filefrag to work out how fragmented a file is, which is
handy for large files, no so handy for lots and lots of small files.

May be not what you were after, but I hope it helps a bit.

-- 
Douglas Furlong
Systems Administrator
Firebox.com
T: 0870 420 4475        F: 0870 220 2178