Path: utzoo!yunexus!maccs!cs3b3aj From: cs3b3aj@maccs.McMaster.CA (Stephen M. Dunn) Newsgroups: comp.sys.ibm.pc Subject: Re: Cache & Buffers..how many buffers are required? Summary: Without cache, too many buffers can hurt performance Message-ID: <2468@maccs.McMaster.CA> Date: 21 Apr 89 00:27:26 GMT Article-I.D.: maccs.2468 References: <2082@uwovax.uwo.ca> <9235@b-tech.ann-arbor.mi.us> Reply-To: cs3b3aj@maccs.UUCP (Stephen M. Dunn) Organization: McMaster U., Hamilton, Ont., Can. Lines: 24 In article <9235@b-tech.ann-arbor.mi.us> zeeff@b-tech.ann-arbor.mi.us (Jon Zeeff) writes: >A simple test is not going to tell you how many buffers to use. I have one >system that needs > 50 because of a large directory. The system just crawls >with fewer buffers. The only thing is, if you don't need that many, you shouldn't have that many (which I guess is why you said that the user should test it out with varying numbers of buffers). On machines with slow processors (XTs, mostly), the overhead in searching excessive numbers of buffers can actually slow the machine down in disk accesses. I don't know the magnitude of this effect, but I imagine it would be noticeable in very disk-intensive programs. The rule of thumb I've heard is that unless you have reasons to do otherwise, 12-15 buffers is about right. Of course, the other argument against using lots of buffers is that they eat up memory, but many people have more memory than they know what to do with (software developers excluded). -- ====================================================================== ! Stephen M. Dunn, cs3b3aj@maccs.McMaster.CA ! DISCLAIMER: ! ! This space left unintentionally blank - vi ! I'm only an undergrad ! ======================================================================