A method and system of managing performance of data transfers for a data access system providing data transfers from content servers to remote users in response to user requests, includes calculating performance data summaries at least at a subset of the user sites and transmitting the data for receipt for remote summarization and storage. The data include information indicative of transfer size, throughput, transfer time, source, time and date. The method and system include selecting a quantity of the performance data received, preferably over a time interval, and summarizing and storing the data. Further summarizes can also be calculated. The data may be used to ascertain conditions and manage the performance of the data access system. In the preferred embodiment, the method and system measure performance of Internet HTTP server applications. The method and system can monitor the performance of a plurality of data access systems, selecting performance data depending on the source of the data transfer for separate summarization and storage thus enabling a high volume of data transfer monitoring.