Subject: USL Capacity Planning Spreadsheet - Google DocsSince I don't use Google Docs myself, I wasn't sure how the regression analysis of the inverted USL transform (2nd degree polynomial) was done. The Google tool does not have the full equivalent of the Excel AnalysisPak. Scott explained that he was able to hack it with LINEST(), just like Excel. Cool!
Date: Sun, 26 Jul 2009 19:46:44 -0400
From: Scott Roberts
I've used your scalability model quite frequently over the past few years, and I've recently converted them over to Google Spreadsheets. Since the various Google-supplied graphing facilities do not provide trend lines (much less the polynomial variety), I had to automate the regression calculation for each deviation point for the chart. The result is less smooth than an Excel trend line but it gets the job done. The upside of all this is that the USL parameter coefficients are now automatically calculated. Simply plug in the number of virtual users, transaction rate, and response time, and let the spreadsheet handle the rest.
Scott has kindly provided 3 examples, which you can also use:
- Spreadsheet derived from the Guerrilla Capacity Planning textbook.
- Load Generator example taken from "Benchmarking Blunders and Things That Go Bump in the Night," CMG MeasureIT, 2006.
- Conversion of the GCaP class Excel sscalc-class.xls spreadsheet.
Thank you, Scott!