an approximation to an n-server capacity planner

an approximation to an n-server capacity planner - A little...

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A little elaboration of capacity planning Dennis Shasha
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Capacity Planning Arrival Rate A1 is given as an assumption A2 = (0.4 A1) + (0.5 A2) A3 = 0.1 A2 Service Time (S) S1, S2, S3 are measured Utilization U = A x S Response Time R = U/(A(1-U)) = S/(1-U) (assuming Poisson arrivals) Entry (S1) 0.4 Search (S2) Checkout (S3) 0.5 0.1 Getting the demand assumptions right is what makes capacity planning hard
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How to Handle Multiple Servers Suppose one has n servers for some task that requires S time for a single server to perform. The perfect parallelism model is that it is as if one has a single server that is n times as fast. However, this overstates the advantage of parallelism, because even if there were no waiting, single tasks require S time.
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Servers There are two components to response time: waiting time + service time. In the parallel setting, the service time is
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an approximation to an n-server capacity planner - A little...

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