Re: What Is Scalability?

Hi, I think that "software scalability" is the measure on how an application could accomodate a large number of simultaneous users without requiring internal architecture refactoring. It's not about speed, it's not about technology, it's about architecture. I also think that maintenance and development time are not attributes of scalability - but of the architecture. We can even make a simple comparision between scalability and the law of Demeter (low coupling) - the scalability of an architecture is reversely proportional with the number of message pipelines between it's layers. That means that a simple architecture (like PHP/Perl) will accomodate much simpler a large number of users because it's messages can be very simply "mirrored" horizontally - adding CPU power and RAM. An application built on complex architecture (Java with RMI, direct memory access between threads, etc) will require a very complex architecture refactoring to support horizontal scaling. Anyway - I am also supporting MVC software development in PHP from the same reason - low coupling between layers that will lead to ease of development and maintenance. My 2c Alexandru -- Alexandru COSTIN Chief Operating Officer http://www.interakt.ro/ +4021 312 5312 "Chris Shiflett" <shiflett@php.net> wrote in message news:20031019232233.59655.qmail@web14301.mail.yahoo.com... > PHP has been both heralded and criticized on a number of topics. This is to be > expected, considering the rate of growth of PHP's popularity. It has given > people something to talk about. > > One topic that seems to come up a lot is scalability. ONJava.com has an > interesting article entitled The PHP Scalability Myth: > > http://www.onjava.com/pub/a/onjava/2003/10/15/php_scalability.html > > Of particular interest to me is the variety of definitions for scalability that > I have noticed, both in this article and elsewhere. I wrote a brief description > of what scalability is to me in my blog (http://shiflett.org/). > > How do you define scalability? What factors do you consider when you declare > whether a particular technology is scalable? Do you think PHP is scalable? Does > Yahoo? > > Chris > > ===== > My Blog > http://shiflett.org/ > HTTP Developer's Handbook > http://httphandbook.org/ > RAMP Training Courses > http://www.nyphp.org/ramp