WEEK 8

WEEK 8

Capacity Management

Synopsis

We consider issues of identifying demand, customer activities, analyzing process designs for capacity implications, and capacity management in e-Services.

Readings

Nature of e-Services Capacity Management

This first short article addresses the key question for us to consider, and covers the simplest case of capacity management, in which the digital content is static, and server duties are fairly homogeneous and thus interchangeable.

(Required) “How do the large web sites handle the load of millions of visitors per day?” HowStuffWorks.com

http://www.howstuffworks.com/question342.htm

The next short article indicates the two halves of the capacity management problem, leading to two approaches being needed to study an e-Service’s capacity.

(Required) Butler, J., “E-Performance Management Gains Attention at CMG,” Software Magazine, May 8, 2000.

http://www.softwaremag.com/archive/2000feb/CMG.html

This Microsoft White Paper provides an overview of capacity planning projection methods for dynamic e-Services (both B2C and B2B) on the WWW. The methods described are for making projections about the feasible site capacity.

I would suggest that you start at the end of the article – which is a Case Study of capacity planning issues at MSNBC – then go back to the front end and read until you get techied-out (in the middle, many calculations are presented, for which you may not have the patience or interest). Note all of the additional e-Service capacity types mentioned in the first page of the article. If you are interested in some of these other capacities, such as how a third-party payment service can affect a site’s performance, or how to track users within a site to gauge their capacity use, you may want to read Philip Greenspun’s book at http://www.arsdigita.com/books/panda/, which humorously discusses the difficulties involved with each.

(Required – At Least the Non-Technical First Half, and the MSNBC Case Study) “Capacity Planning,” Microsoft White Paper

http://www.microsoft.com/technet/ecommerce/capplan.asp?a=printable

If you are using Netscape Navigator to print this out, you may not have the following embedded in the document, due to its lack of support for inline frames:

Click here to download a page with all of the missing Figures.

Automated Analysis of Demand Loads

One approach to testing a web site (or any other e-Service) before it goes live is to have actual humans within your company test the site out, by generating demand loads for the site. This approach has numerous shortcomings, as you can imagine, which are documented on many of the sites below.

The natural way to improve on the above approach is through automated tools for capacity management. The approach is described very briefly in the short Entrepreneur Magazine article. Basically, for each of the tools below, a manager would set up the real website’s service-process configuration, test the site with “real” demand loads generated by a demand-load simulator, and after adjusting the site’s performance, make the site go into operation. The MercuryInteractive articles lay out various issues that are important in (i) load testing before going live, and (ii) monitoring performance after going live. If you are interested in additional examples of such technology, the links to tools found below present similar tools.

(Required) “Stress Test for Web Sites That Won’t Affect Live Performance,” Entrepreneur Magazine

http://www.entrepreneur.com/Your_Business/YB_SegArticle/0,1314,279364-8----,00.html

(Required) “Load Testing to Predict Web Performance”

http://www-svca.mercuryinteractive.com/products/whitepapers/load_testing/index.html

(Optional – Browse/Read) “Isolating Bottlenecks with Performance Monitors”

http://www-svca.mercuryinteractive.com/products/loadrunner/lrdoc/index.html

(Optional - Browse) Monitoring Points within an e-Service-Process

http://www-svca.mercuryinteractive.com/products/loadrunner/lrdoc/supported.html

(Optional – Browse/Read) “What is Web Performance Monitoring?”

http://www-svca.mercuryinteractive.com/products/monitoring/

A variant of this approach is to use actual consumer computers – based on a peer-to-peer strategy – to study a site under actual Internet traffic conditions from actual users’ desktops.

(Optional) “Load Testing Uses Distributed PCs -- Exodus service generates loads from users in peer-computing mode”

http://www.techweb.com/se/directlink.cgi?INW20001113S0019

Another approach – not considered here – is to formally model the system using OR-based mathematical tools for queueing networks, which might not do you much good in a turbulent e-Service competitive environment, and might require you to employ someone with a PhD in that topic. If you are interested in this approach, I suggest you buy a book by Daniel A. Menasce and Virgilio A. F. Almeida, either Capacity Planning for Web Performance (1998) or Scaling for E-Business (2000).

Interestingly, I haven’t found any tools that use a software model of both the client (i.e., “virtual users”) and server (i.e., “virtual service-process”) sides to do capacity analysis, as with the Operations Support Systems we read about during Session 3 for network management.

Tools for Load Testing and Web Performance Monitoring

GomezNetworks Methodology

http://www.gomeznetworks.com/mktg/method/method1.asp

“Rational Software Introduces Rational SiteLoad; Industry’s First Web-Based Load Testing Product,” Press Release, August 28, 2000.

http://www.rational.com/news/press/pr_view.jsp?ID=7978

Data Sheet: SiteLoad - http://www.rational.com/media/news/presskit/siteload.pdf

http://www.rational.com/products/siteload/readme.jsp

“What is Web Performance Monitoring?”

http://www-svca.mercuryinteractive.com/products/monitoring/

Product: ActiveWatch - http://www-svca.mercuryinteractive.com/products/activewatch/

Product: Topaz - http://www-svca.mercuryinteractive.com/products/topaz/

Rapoza, J., “SilkPerformer Tests Web-Site Fabrics,” PC Week, July 29, 1999.