Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!mnetor!seismo!husc6!harvard!panda!genrad!decvax!cwruecmp!nitrex!rbl From: rbl@nitrex.UUCP Newsgroups: net.unix-wizards Subject: Re: RAM disk vs paging + buffer cache Message-ID: <381@nitrex.UUCP> Date: Wed, 13-Aug-86 12:33:19 EDT Article-I.D.: nitrex.381 Posted: Wed Aug 13 12:33:19 1986 Date-Received: Thu, 14-Aug-86 08:41:31 EDT References: <514@opus.nbires.UUCP> Reply-To: rbl@nitrex.UUCP ( Dr. Robin Lake ) Organization: The Standard Oil Co., Cleveland Lines: 31 About 12 years ago, I developed a solid-state disk marketed by Monolithic Systems Corp. of Englewood CO. (Known as EMU for 'extended memory unit'.) One of my graduate students at Case Western Reserve did a dissertation on UNIX performance enhancements using this disk --- which works much like a RAM disk. Turned out that one of the best strategies was to have TWO disks (since a dual-ported version was available, one could have one unit partitioned and two controllers). One partition was for /usr/tmp and the other was to hold the root. Idea was that frequently used system programs would have greatly reduced latency and that the user's scratch space would be similarly sped up. Note: if a device driver is required, much of the inherent speed advantage is lost. Drivers consume milliseconds per access, not very noticible when disk latency is tens to hundreds of milliseconds. When RAM is accessed, rotational and seek latency go away and the driver delays are very noticable. By the way, the solid-state disk enabled us to do some real-time applications of UNIX very nicely. A 1 million sample/sec analog-to-digital converter was one of these. Robin B. Lake Standard Oil Research and Development 4440 Warrensville Center Road Cleveland, OH 44128 (216)-581-5976 cbosgd!nitrex!rbl cwruecmp!nitrex!rbl