End-User Web AvailabilityMeasuring AvailabilityExperimentResultsPut Another WayClient Hardware Problems Dominated User ExperienceWhat About Speed?Does Retry Help?What Guides Retry?End-User Web AvailabilityMatthew Merzbacher(visiting researcher UCB CS)Dan Patterson(undergraduate UCB)Measuring Availability• Measuring “nines” of uptime is insufficient– Reflects unrealistic operating conditions• Need to capture end-user’s experience– Server + Network + Client• Client Machine and Client SoftwareExperiment• “Hourly” small web transactions from two sites (Mills CS, Berkeley CS)• To a variety of sites, including– Internet Retailer (including international sites)– Search Engine– Directory Service (also including int’l sites)• Ran for 6+ monthsResults• Success, completeness, and speed.999911.0000.99845.99945Ignoring client, network, and one-time errors.999721.0000.99756.99908Ignoring client and network problems.98569.99349.98870.98877Ignoring client problems.92668.93456.93108.93049RawDirectorySearchRetailerAllPut Another WayClient Errors Medium Network TrafficSevere Network Traffic Server ErrorsCorporate ErrorsClient Hardware Problems Dominated User Experience• System-wide crashes• Administration errors• Power outages• And many many more…What About Speed?01020304050600.95 0.96 0.97 0.98 0.99 1AvailabilityTime (sec)retailersearchdirectoryDoes Retry Help?n/a1.000.312500.42105Corporate0.961.000.785710.91111Server0.688891.000.923080.78947Severe Network0.831780.928570.870370.86207Medium Network0.264710.264710.270590.26667ClientDirectorySearchRetailerTotalError TypeWhat Guides Retry?• Uniqueness of data• Importance to user• Loyalty of user• Transience of information• And