Path: utzoo!news-server.csri.toronto.edu!cs.utexas.edu!usc!samsung!crackers!m2c!umvlsi!dime!dime.cs.umass.edu!moss From: moss@cs.umass.edu (Eliot Moss) Newsgroups: comp.protocols.nfs Subject: Re: Incremental sync()s and using disk idle time Message-ID: Date: 12 Mar 91 02:22:52 GMT References: <28975@cs.yale.edu> <10773@dog.ee.lbl.gov> <3236@crdos1.crd.ge.COM> Sender: news@dime.cs.umass.edu Reply-To: moss@cs.umass.edu Followup-To: comp.protocols.nfs Organization: Dept of Comp and Info Sci, Univ of Mass (Amherst) Lines: 27 In-reply-to: davidsen@crdos1.crd.ge.COM's message of 11 Mar 91 13:19:31 GMT In article <3236@crdos1.crd.ge.COM> davidsen@crdos1.crd.ge.COM (Wm E Davidsen Jr) writes: As long as there's a working sync or other means for my process to do ordered writes in that less than one percent of the time when I care, I am delighted to have things done in the fastest possible way the rest of the time. The only time I ever care is when doing something like database or T.P. where order counts in case of error. If I'm doing a compile, or save out of an editor, or writing a report, as long as what I read comes back as the same data in the same order, I really don't care about write order (or byte order, bit order, etc) on the disk. There is a problem with this reasoning, which is the assumption that the design and tuning worked out by the manufacturer is anything like what *you* need for *your* application mix. And in many cases the *design* is limiting and there is no way to tune it the way you need. What I am getting at is not just the semantic requirement that certain things be written (or not written) to disk at certain points or in certain orders, but performance requirements related allocation and I/O scheduling. Just because something works nicely for a time sharing mix does not mean it's reasonable for databases, etc. -- J. Eliot B. Moss, Assistant Professor Department of Computer and Information Science Lederle Graduate Research Center University of Massachusetts Amherst, MA 01003 (413) 545-4206, 545-1249 (fax); Moss@cs.umass.edu