Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!asuvax!anasaz!qip!john
From: john@qip.UUCP (John Moore)
Newsgroups: comp.benchmarks
Subject: Re: How do maxed out users compare to users with think times
Message-ID: <6648@qip.UUCP>
Date: 13 Jun 91 15:23:34 GMT
References: <676640053.AA19240@flaccid> <4046@sixhub.UUCP>
Organization: Anasazi, Inc.  Phoenix, Az
Lines: 34

In article <4046@sixhub.UUCP> davidsen@sixhub.UUCP (bill davidsen) writes:
]In article <676640053.AA19240@flaccid> tonys@pyra.co.uk (Tony Shaughnessy) writes:
]
]| How do I calculate how many real life users these 100 maxed out users simulate?

We have been doing extensive benchmarking to predict hotel reservation system
behavior. Our approach is as follows:
  -run the benchmarks with simulated "maxed out users." Measure the
   transaction rate that is sustainable with acceptable response time.
  -observe real users and measure their "think time"
  -ratio to determine numbers of users we can support

Typical numbers for one configuration:
  -max TPS: 10
  -think time per user 27 seconds
  -equivalent max number of users 270

Note that the definition of a "transaction" is critical here. If you are
using a system where every keystroke is a "transaction," things are likely
to get wierd.

By the way, our benchmarking has been testing commercial relational databases
(which must remain unnamed) on Unix super-mini multi-cpu systems. We find
(surprisingly on first blush, reasonable with analyses) that performance is 
limitted by CPU speed, not I/O bandwidth. We also find that performance 
increases linearly with the number of CPU's up to some number, after
which the increase per CPU is much smaller. This implies that there
are critical bottlenecks in the database software.
-- 
John Moore HAM:NJ7E/CAP:T-Bird 381 {ames!ncar!noao!asuvax,mcdphx}!anasaz!john 
USnail: 7525 Clearwater Pkwy, Scottsdale,AZ 85253 anasaz!john@asuvax.eas.asu.edu
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