linux-ext4 - Re: e2defrag 0.81 released

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Date:	Sat, 7 Jul 2012 00:02:26 -0600
From:	Andreas Dilger <adilger@...ger.ca>
To:	Phillip Susi <psusi@...ntu.com>
Cc:	ext4 development <linux-ext4@...r.kernel.org>
Subject: Re: e2defrag 0.81 released

On 2012-07-06, at 5:01 PM, Phillip Susi wrote:
> Back in the days when dinosaurs walked the earth ( the '90s ), there was
> a defragger for ext2 written by Stephen Tweedie with contributions from
> others including Ted Ts'o.  After many years of abandonment and bit rot,
> I have decided to take over maintainership of the package.  I now feel
> that it is in good enough of a state for a wider audience ( including
> working with extents and other ext4 features ), so I am announcing it
> here and asking for testing.  The project page is
> http://launchpad.net/e2defrag.
> 
> The program opens an unmounted block device and parses the filesystem
> itself, assigns new locations for all blocks, packing them to the left
> within their native block group if possible, then moves all the blocks
> around quickly and efficiently.  The process it fast, but unsafe: should
> anything go wrong or the process be interrupted, your fs will be toast.

I hate to rain on your parade, but, are you aware of e4defrag?

It is already in e2fsprogs, and can be used on a mounted ext4 filesystem...
It also needs some lovin' to make it really robust, but would definitely
be a better starting point than the ancient e2defrag code...

That's why it is always a good idea to post to the mailing list _before_
you start on a project, to see what else is going on...  Definitely there
is a need for such a tool, but I hate to see effort being spent in two
different directions to make two so-so tools, when it could be going in
the same direction to make one excellent tool.

Cheers, Andreas

> Therefore:
> DO NOT USE ON A FS YOU CARE ABOUT AND/OR HAVE NOT BACKED UP FIRST
> 
> Should a bug cause it to trash your fs, a raw e2image ( e2image -r
> /dev/sda1 - | bzip2 -c > sda1.e2i.bz2 ) made before the defrag, and
> obviously saved on another fs, would be most helpful in debugging.
> 
> One of the more interesting features is the ability to pass a list of
> inodes to be given priority over others.  This can be used to pack a set
> of files together at the start of the disk to allow for faster booting.
> I cobbled together a simple python script, dump2inodes, that can obtain
> the list of files that ureadahead ( Ubuntu ) loads during boot and
> generates the inode priority listing you can pass to e2defrag, and this
> gives some nice boot time improvements.
> 
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Cheers, Andreas






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