You're most probably right. Nonetheless, I still believe that *in
theory*, taking disk geometry into account, you can improve speed.
However, the gain would be marginal and at the loss of CPU.
Anyway, it's not really my field of expertise, so I actually shouldn't
be having this discussion with you ;).

The problem is indeed with the software scheduler. Due to misaligment,
one page on the initiator would require two pages on the target.

Kind regards,


On Dec 22, 5:39 pm, "Ulrich Windl" <ulrich.wi...@rz.uni-regensburg.de>
> On 22 Dec 2008 at 5:11, Eric wrote:
> > Besides that, I don't think I totally agree on your statement. Letting
> > the IO scheduler taking the actual disk geometry into account, should
> > give more performance. However, the fdisk default values are probably
> > standard for disks these days.
> The disk scheduler can safely assume that contiguous nearby "forward" requests
> perform better than small scattered "backwards" requests. All other is mostly
> speculative IMHO. You would have to know about the heads position relative in
> time, track skew, sector skew, etc. Today's disk have cache big enough for 
> whole
> tracks, so the scheduler shouldn't really care about sectors. Also the 
> scheduler
> really cannot know on which physical cylinder (or track, or head) a specific 
> block
> will actually reside.
> However when we are talking about problems in the scheduler _software_ you 
> may be
> right. I didn't look into it for years ;-)
> Regards,
> Ulrich
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