hole punching performance

[Bradley C. Kuszmaul]

So my understanding is that the first time I do a read() I'll have to read
the extents.  My writes are on the order of a megabyte, a 250MB file will
likely require an extra I/O to open.  That's fine.

It really has been helpful to have all this performance-modeling
information.

Thanks.

-Bradley

On Tue, Jan 15, 2013 at 5:54 PM, Dave Chinner <david at fromorbit.com> wrote:

> On Tue, Jan 15, 2013 at 04:34:50PM -0500, Bradley C. Kuszmaul wrote:
> > So does it cost a lot to read all the extents just to read the first
> block?
>
> Depends on the number of extents in the file. Figure an IO per 250
> extents for a 4k block size filesystem (extent records are 16 bytes
> in size on disk).
>
> Cheers,
>
> Dave.
> --
> Dave Chinner
> david at fromorbit.com
>
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