On Mon, 2007-10-29 at 09:22 -0400, Bill Davidsen wrote:
> > consider a storage with 64 spt, an io size of 4k and partition starting
> > at sector 63.
> > first io request will require two ios from the storage (1 for sector 63,
> > and one for sectors 64 to 70)
> > the next 7 io (71-78,79-86,97-94,95-102,103-110,111-118,119-126) will be
> > on the same track
> > the 8th will again require to be split, and so on.
> > this causes the storage to do 1 unnecessary io every 8. YMMV.
> No one makes drives with fixed spt any more. Your assumptions are a
> decade out of date.
Your missing the point, it's not about drive tracks, it's about array
tracks, aka chunks. A 64k write, that should write to one and only one
chunk, ends up spanning two. That increases the amount of writing the
array has to do and the number of disks it busies for a typical single
I/O operation.
--
Doug Ledford <dledford@xxxxxxxxxx>
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http://people.redhat.com/dledford
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