I have a vague recollection that early time sharing systems, in particular UNIX, enforced I/O fairness by fragmenting files and thereby freeing the I/O between fragments. However I don't recall much and this might be an artifact of aging :-) If so, I am curious as to how this was implemented - interleaving sectors or some more complex physical fragmentation or ?? Anyone point me to any references? Tom PS: as in infrequent poster I am happy to make a small change to the statistics