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On Wed, 13 Jul 2005, Mike Cheponis wrote:

> On Wed, 13 Jul 2005, James Buchanan wrote:
>
>> Since we can't know the physical disk geometry on modern disks,
>
> I don't believe this is true.
>
> If one were willing to measure transfer rates for a variety of sectors, I=
=20
> suspect an exact map of the disk could be determined.

 =09Useful reference for this:

 =09http://www.pdl.cmu.edu/PDL-FTP/DriveChar/traxtent.pdf

 =09    Track-aligned extents (traxtents) utilize disk-specific
 =09    knowledge to match access patterns to the strengths of
 =09    modern disks. By allocating and accessing related data
 =09    on disk track boundaries, a system can avoid most ro-
 =09    tational latency and track crossing overheads. Avoiding
 =09    these overheads can increase disk access efficiency by up
 =09    to 50% for mid-sized requests (100=E2=80=93500 KB). This paper
 =09    describes traxtents, algorithms for detecting track bound-
 =09    aries, and some uses of traxtents in file systems and video
 =09    servers.

--=20
 =09=09David/absolute       -- www.NetBSD.org: No hype required --
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