Originally posted by slimdave
What if you chose volume of PIO's, or duration of PIO waits? I think I'd be happier with that.
Yes, better - but still silly to focus on just one statistic.

If you blindly minimise PIO you might end up back where we started with Millsap's LIO/PIO ratio of 99.99999999 . . . .
I can't say I've ever seen that in my Oracle applications - but I did have a problem with Rdb under VMS: version 1 would thrash the disks for 5 minutes then the CPU would go to 100% and stay there for days (I'd cancel it on Monday morning); I could rewrite it as version 2, which would churn the disks for 30 minutes an then give the result (I think the optimiser was sensitive to litterary style!).
I suspect that version 2 did more PIO, but I had neither the tools nor the expertise to prove it.

There is no silver bullet. Over and out.