In a Grid computer system having a plurality of download servers in network communication with client computers and a download management system, a client requests a download plan from the download management system for downloading data in parallel from the plurality of download servers to a client. The client requests chunks of data from download servers identified by the download plan. The client monitors the performance of the download servers downloading the chunks and reassigns portions of chunks amongst the download servers in order to improve the performance of completing the download of the chunks. A chunk of download data is a plurality of files, a file or a portion of file of data.