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Physical IO Cost vs Logical IO Cost

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As far as I know the ASE optimiser estimates a physical page read as 18 and a logical page read as 2.

This suggests the cost of a physical read is only 9 times greater than a logical read.

 

In the real world (or at least my world) a physical page is between 2ms and 18ms depending on the SAN tier, what time of day it is, etc

And a logical page is about 0.05ms. So at best a physical page read is about 50 times slower and at worse 300 times slower.

 

Shouldn't we adjust these values for the world as it is now ? ie logical read should be set to 2 and a physical read should be set between 100 and 300.

 

Is it possible to change these values to something reflecting our own environments ?

I don't think these timings are that unusual.


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