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Ok, as probably you have seen, I just committed an XrdClient test version able to do async reads. Here are some considerations: - async read ahead is enabled iff async mode is enabled (GO_ASYNC param) - note that from now on, xrootd streamIDs and Logical Connection IDs are not the same anymore, but they are linked through the XrdClientSid stuff. A Logical connection can have as many stream ids it wants, and can treat them together. - XrdClient is able to handle max 65535 pending operations at a time - a pending operation is a "normal" sync command stream or a pending async request. At this time only reads are async-implemented. - any application can request the server to send data (which will go into the client side cache) through the Read_Async(offs, len) method. So, this is the right path to follow if you have a long prefetch list. The result code will tell you if you run out of streamids. - you don't know when the async requested data will be delivered, neither the order in which a prefetch list will be delivered. They are all parallel and quite random even in simple apps. Here are some other considerations: - the actual read ahead algorithm is too trivial, smart apps like xrdcp (which runs at optimal speed with its own big buffer) generate some network overhead. - slow apps, which "think" between consecutive reads will hopefully get the maximum benefit, because the data will arrive while they think. What to do now? If you are curious you can play with the current version. In the meantime I will integrate the latest patch for xrdcp and think about a readahead algorithm which has to be smarter but not too much complex. Fabrizio -- -------- Fabrizio Furano INFN - Istituto Nazionale di Fisica Nucleare [log in to unmask]