Can somebody explain this? du & ls showing different sizes

[Patrick O'Callaghan]

On Fri, 2009-02-20 at 13:15 -0800, Leslie Satenstein wrote:
> 
> 
> --- On Mon, 2/16/09, Patrick O'Callaghan <pocallaghan at gmail.com>
> wrote:
>         From: Patrick O'Callaghan <pocallaghan at gmail.com>
>         Subject: Re: Can somebody explain this? du & ls showing
>         different sizes
>         To: fedora-list at redhat.com
>         Date: Monday, February 16, 2009, 8:45 AM
>          
>         On Mon, 2009-02-16 at 07:13 +0000, Vijay Gill wrote:
>         > 2009/2/16 Patrick O'Callaghan <pocallaghan at gmail.com>:
>         > > On Sun, 2009-02-15 at 23:45 +0000, Vijay Gill wrote:
>         > >>  > That could be because you're using XFS.
>         > >> >
>         > >> > poc
>         > > [...]
>         > >> Thanks but how does that statement explain the behaviour I am
>         seeing?
>         > >
>         > > I'm
>          reaching here, but since XFS uses allocation strategies
>         different
>         > > from the more familiar ext3 system, I wondered if 'du' could
>         in some
>         > > circumstances report larger numbers than "normal".
>         > >
>         > > Apologies if I'm raving.
>         > >
>         > > poc
>         > >
>         > > --
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>         > >
>         > 
>         > You are spot on Pat. XFS allws you to pre-allocate contiguous area of
>         > disk for a file when it is opened for writing data. This is determined
>         > by allocsize parameter during mount and is used foe reducing
>         > fragmentation(fragmentation in Linux? yes siree, it does happen in
>         > Linux too).
>         > 
>         > In my case I have provided 1M
>          which is far much less than 512M which
>         > XFS is pre-allocating. This is what caught my eye.
>         
>         It's nice to have one's intuition confirmed once in a while :-)
>         
>         poc
>         
>         Hi Poc
>         
>         Where is the overallocation parameter stored? 
>         
>         Poc, I appreciate your expertise in the answers, but when you answer something about Linux,
>         note that I have not your ideas of where to look for settings.
>         Therefore, I am sure readers would like a hint about the directory/file in which this info
>         is stored.
>         
>         Thanks and have a good weekend.
>         
>         Leslie 

Actually I don't claim any specific expertise regarding XFS, but when
you mess about with operating systems and filesystems for many many
years, you develop a certain feeling for how things are likely to work
(there's nothing new under the sun). As to where XFS stores the
"overallocation parameter", I've no idea but the first place I'd look
would be in the filesystem superblock, not in any file or directory.

Or as a last resort you could always read the manual ...

poc

PS Please don't post in HTML. I can't edit it sensibly, which is why I
just tacked a reply on the end. It's also contrary to the Guidelines of
this list.