Path: utzoo!mnetor!uunet!husc6!think!ames!ucbcad!ucbvax!jade!eris!mwm From: mwm@eris.BERKELEY.EDU (Mike (My watch has windows) Meyer) Newsgroups: comp.os.misc Subject: Re: OS features Message-ID: <6315@jade.BERKELEY.EDU> Date: 16 Dec 87 22:13:00 GMT References: <561@amethyst.ma.arizona.edu> <3228@tut.cis.ohio-state.edu> Sender: usenet@jade.BERKELEY.EDU Reply-To: mwm@eris.BERKELEY.EDU (Mike (My watch has windows) Meyer) Distribution: na Organization: Missionaria Phonibalonica Lines: 27 Mark Woodruff writes: > o Contiguous file allocation on large devices. The additional overhead > of discontiguous file allocation is unwarranted on modern hardware. Unicos (Cray's System V for their hardware) has transparent support of files with large contiguous chunks, and an IO system that takes advantage of them. Each unix file system is broken up into two or more partitions (these aren't unix partitions, but are more like the BSD cylinder groups). The first partition is dedicated to special files, most notably directories. Blocks for a data file are allocated contiguously as long as no one else needs blocks in the partition. File creation round-robins through all but the first partition of the file system, to give the processes writing each file as much time as possible to grow the file. Unicos also supports disk striping. The results work fairly well, but I don't know how much is do to which activity.