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On Dec 1, 2003, at 3:11 PM, Thor Lancelot Simon wrote:

> Matt Thomas suggested simply starting at whichever end of the other
> queue is nearer the current head position, which is an interesting
> idea.  I was pondering zoning the disk, so you'd have multiple "queues"
> on each side of the "delayed"/"normal" divide, and could try to switch
> to the one nearest the block you're currently at, but that adds
> significant complexity.  I'm going to implement a couple of different
> things and measure them for different workloads.

Presumably this would imply recording the block # of the last request 
that was issued on the disk?

I can see a danger in this kind of algorithm... if you were to always 
prefer issuing requests for "near by" blocks, then you could get into a 
situation where an app that performs many transactions to a localized 
region could starve other apps whose data is "somewhere else".

         -- Jason R. Thorpe <thorpej@wasabisystems.com>

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