Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!linus!decvax!harpo!seismo!hao!hplabs!sri-unix!edhall@rand-unix From: edhall@rand-unix@sri-unix.UUCP Newsgroups: net.unix-wizards Subject: Re: Re: Ram disks Message-ID: <3796@sri-arpa.UUCP> Date: Wed, 3-Aug-83 21:46:00 EDT Article-I.D.: sri-arpa.3796 Posted: Wed Aug 3 21:46:00 1983 Date-Received: Sat, 6-Aug-83 04:00:31 EDT Lines: 28 You probably do not want them to extend virtual memory (paging/swapping). We do get close to the same performance (I think) by utilizing paging/swapping area on disks that are isolated from the rest of our system I/O. Most of the 11/70's swap on RK05's that have their own controller (the additional drives on this controller are seldom used). Whoa!! I thought that swapping is best done on your FASTEST disks. An RK05 is SLOW, no matter whether it is exclusively used for swapping or not. I once experimented with this on a PDP-11/45 running V7 by moving swapping from an AMPEX-980 (with a one-of-a-kind controller) to an RK05. Even though the AMPEX supported all filesystems as well as usually serving as swap, moving swap off to the RK05 slowed things down considerably; I immediately received a barrage of complaints as to how the already slow system had gotten much slower. Admittedly, an 11/70 with large memory is not going to be swapping as much as this 11/45 was. But speeding up the swapping process can be quite significant on a system that needs to swap. And on a paging system, disk I/O speed can be even more important. How a `ram disk' is best used depends upon the system and what it is used for. -Ed Hall edhall@rand-unix {ucbvax,decvax}!trw-unix!randvax!edhall