...all this data will be distributed to a handfull of TIER1 sites (CERN is TIER0) all over the world (about 10). At the TIER1 sites the data will be preprocessed. The TIER1 sites distribute their preprocessed data to TIER2 sites which are the places where the international scientists work. I work at a TIER1 site and we face a lot technical challenges with this project. At a TIER1 site as I mentioned, the data is preprocessed too, so we will need a compute cluster and the necesary bandwith internally to move the data around. With each new software release (about every six months), ALL raw data has to be reprocessed with the new software. All results have to be stored. So for every part of raw data we will have to store preprocessed data for every software release. Of course a lot of data will be stored on tape but we expect that the dataflow from CERN (for us 150MB/s to disk and 75 MB/s to tape) will be the least of our problems. Moving the data around and preprocessig the data is probably a bigger problem in the long run. An the fact that the machine will be running for about 15 years or so, this will be a very long run!