Re: [PATCH 0 of 3] [RFC] I/O Hints

[Andreas Dilger <adilger@xxxxxxx>]

On Jun 05, 2008  11:40 +0100, Jamie Lokier wrote:
> >From a database perspective, I'm thinking it would be very useful to
> provide similar information for large files.  Database engines have
> the same requirement to know stripe width etc., and filesystems
> allocate large contiguous extents so it it makes sense to pass the
> device characteristics up to the app, with appropriate offset.
> 
> (Same for loopback devices.)
> 
> This is an extreme example of different properties in different offset
> ranges - it depends on file allocation.
> 
> Is there scope to extend FIEMAP to pass this sort of information?

I have ideas in that direction, but have been gun-shy about presenting
them until the existing controversy dies down...  I think it is actually
fairly straight forward to enhance FIEMAP to allow arbitrary file layouts
to be returned to an application.

Cheers, Andreas
--
Andreas Dilger
Sr. Staff Engineer, Lustre Group
Sun Microsystems of Canada, Inc.

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