If you are interested in mirroring part of a server you control, perhaps to improve reliability by providing alternatives, then there are many available mirroring tools. Keep in mind such simple possibilities as (under Unix) a cron job that tars and compresses the web site on the "master" server at a particular time of day, and another cron job on the "slave" server which takes advantage of the lynx browser to retrieve that document, then uncompresses and untars it. For many purposes, such simple mirroring setups are effective and near-foolproof.