> This would imply that an upgrade in drive RPM should be accompanied by
> a decrease in random_page_cost, correct?

Maybe.  Maybe not.   Tom's Hardware did some Bonnie++ testing with a variety 
of new drives last year.   They were moderately surprised to find that there 
were "faster" drives (i.e. higher RPM) which had lower real throughput due to 
poor onboard software and hardware, such as a small and slow onboard cache.

So, it would be reasonable to assume that a 10,000 RPM Barracuda could support 
marginally lower random_page_cost than a 7,200 RPM Barracuda ... but that 
tells you nothing about a 10,000 RPM Maxtor Diamond (as an example).

Also, many other factors influence real random_page_cost; the size and access 
pattern of your database is probably much more important than your RPM.

-Josh Berkus
 Aglio Database Solutions
 San Francisco

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