Category Archives: Models

Erlang Units…

Per Wikipedia, an Erlang Unit is: “The erlang (symbol E[1]) as a dimensionless unit is used in telephony as a statistical measure of offered load. It is named after the Danish telephone engineer A. K. Erlang, the originator of traffic … Continue reading →

Posted in Models, Sizing, Tuning | Tagged , | Comments Off

[CheapHA-HPC] Part 1 – First Steps

This is part 1 in a multipart adventure into cost-efficient supercomputing and high availability. By now you’ve probably heard of Beowulf Linux clusters, HPC clusters made from PlayStations, the monsters listed at http://www.top500.org/, Amazon’s EC2/S3, and the like. Well, what … Continue reading →

Posted in J2EE, Java, Legacy, Linux, Models, Perl, Scripts, Sizing, Tuning, UNIX, [CheapHA-HPC] | 2 Comments

Is my server’s run queue too deep? Is it saturated?

***This post refers to time sharing operating systems, specifically UNIX or UNIX-Like operating systems – but is relevant for other operating systems and basic kernel scheduling concepts as well. This is also a fairly gross over-simplification of the many pieces … Continue reading →

Posted in AIX, Linux, Models, Sizing, Solaris, Tuning, UNIX, VMWare | Tagged | 3 Comments

Linear Regression for system resource utilization forecasts

So… You have your performance data. you load it into a spread sheet, and you draw a line through the data points and use that to forecast when your system resources *should* expire. That’s great, but does your system performance … Continue reading →

Posted in Legacy, Linux, Models, Sizing, Tuning, UNIX | 1 Comment

M/M/c queues and legacy JDBC connection pool sizing

So, this is a decent intersection of Computer Science and legacy Java (the *NEW* COBOL) apps using some of Little’s Law, and an M/M/c queuing model… Most recent versions of JDBC drivers allow multiple statements to be issued on a … Continue reading →

Posted in J2EE, JDBC, Java, Legacy, Models, Sizing, Tuning, WebSphere | Tagged , , , , , | 1 Comment