On Tue, 2005-01-25 at 01:26 +0200, Hirsch, Michael wrote:
> Hi,
> 
> I'm probably asking something so obvious ... but I admit that I'm
> somewhat of a beginner.

Actually, the answer isn't so obvious.

> I saw dense files mentioned in some of the publications on the open
> source JFS, but have not found a way of doing this from within the
> docs, the code, the mkfs or the tune utility.  I've tried to trace the
> *SPARSE flags in the fs/jfs and jfsutils.  I've tried searching the
> jfs-*.mbox files on the official jfs website for "sparse" and "dense"
> and "contiguous" but nothing turned up.  Looked through the file
> layout paper which has a great example of a sparse file, but I'm
> looking for a dense example.

jfs on Linux does not support the dense file option.  The docs mention
dense files because the code was originally ported from OS/2, where
dense-file creation was the default behavior.  At the time of the port,
it seemed a reasonable thing to eventually support both dense and sparse
options in Linux, as this would be more compatible with OS/2.  As time
went on, the dense file support was never much of a priority, and it
probably won't be.  Applications that would benefit from dense files can
write a file sequentially when creating it, and get the same behavior.

> I'm running RH ES3 AS update 2, kernel 2.4.21-20.Elsmp on an x86_64
> platform if any of this is relevant.
> 
> Pointers would be appreciated.
> 
> Thanks in advance, 
> Michael.
-- 
David Kleikamp
IBM Linux Technology Center

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