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Here my other important mathematical deduction

Ramine

3/16/2016 9:24:00 PM

Hello.......


Here my other important mathematical deduction

If you read this book that i have read:

Performance by Design: Computer Capacity Planning By Example

http://www.amazon.com/Performance-Design-Computer-Capacity-Planning/dp/...

I have said the researcher in this book is using Queuing with
Multiple-Class Models to model an ecommerce website, but i have not used
his method because i have modeled the M/G/c database servers with
anhyper-exponential service and i have approximate it with
an M/M/c queue(c: is the number of servers), other than that this
book don't learn you as i have learned you that the network
of the ecommerce website is limited by the slowest node..

Other than that:

I have just read the following page, look at the the USL

(Universal Law of Computational Scalability) of Dr. Gunther,
he wrote this: (See: http://en.wikipedia.org/wiki/Neil_... )

--------------

The relative capacity C(N) of a computational platform is given by:

C(N) = N
------------------------------------------
1 + α (N - 1) + � N (N - 1)

where N represents either the number of physical processors
in the hardware configuration or the number of users driving the
software application. The parameters α and � represent respectively
the levels of contention (e.g., queueing for shared resources) and
coherency delay (i.e., latency for data to become consistent) in the
system. The Ã? parameter also quantifies the retrograde throughput
seen in many stress tests but not accounted for in either Amdahl's law
or event-based simulations.

----------

His website: http://www.perfdyn...

If you read carefully , you will see that Dr. Gunther is using this
model to predict scalability after he simulates a relatively small
number of vusers in LoadRunner ( because of licensing costs, it's
cost-effective) and after that he finds the coefficients of the
2nd-degree polynomial (quadratic equation) and then transform
those coefficients back to the USL parameters using the α = b - a
and Ã? = a.

And then he is extrapolating with the USL model to higher loads
to predict scalability.

Now my question follows:

Suppose we have obtained a small number of measured load-points
with Loadrunner or others tools, and we calculated the USL equation
to predict scalability of a webserver , how the USL model can predict
if the scalability/performance is limited by the network bandwidth
and not the server ? I think USL can not predict this.

So USL don't have the power of the Queuing theory that allows
us to deduce more facts that are important such us
the network is limited by the slowest node as i have
learned you on my previous posts.


Thank you,
Amine Moulay Ramdane.
1 Answer

fir

12/8/2011 9:57:00 PM

0

>
> tylko trywialnej 'kwadratowej' detekcji kolizji
> (i to grubo bo kulek jest 200 ramek okolo 100/s
> i fizyka jest 5x na ramke - czyli to leci 100tys
> detekcji kolizji na sekunde)
>
100 tys petli - bo czastkowych sprawdzen kolizji to
wychodziloby 20 mln/sekunde

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