From: Mingming Cao <cmm@us.ibm.com>
Subject: Re: files mapped funny? (related to online defragmentation)
Date: Mon, 21 May 2007 11:00:59 -0700
Message-ID: <1179770459.23003.7.camel@localhost.localdomain>
References: <1179755398.389.24.camel@eric-laptop>
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Cc: linux-ext4 <linux-ext4@vger.kernel.org>
To: Eric <erpo41@gmail.com>
In-Reply-To: <1179755398.389.24.camel@eric-laptop>
Sender: linux-ext4-owner@vger.kernel.org

On Mon, 2007-05-21 at 06:49 -0700, Eric wrote:
> Hi,
> 
> I'm getting strange results when I map out the blocks used in files
> larger than a several thousand KB. I never seem to get any more than
> 1024 contiguous data blocks in a row. 
> 
> Here's a portion of the output of my script when I run it on a 176MB
> file in my home directory:
> ...
> Contiguous chunk 67: 2385568 - 2385591  (24 blocks)
> Contiguous chunk 68: 2385608 - 2386448  (841 blocks)
> Contiguous chunk 69: 2386450 - 2387473  (1024 blocks)
> Contiguous chunk 70: 2387475 - 2388498  (1024 blocks)
> Contiguous chunk 71: 2388500 - 2389523  (1024 blocks)
> ...
>
> Maybe this is a bug in my script? Can anyone explain why this would
> happen?
> 
filefrag command comes with e2fsprogs will print the file fragmentation
info. I guess you can try filefrag -v command and see if that matches
what your scripts reported.

Mingming

> I'm attaching my script in case other ext2/3/4 newbies can get any use
> out of it, and in case anyone needs to see it in order to answer my
> question. It's pretty self-explanatory, though.
> 
> Cheers,
> 
> Eric
>