Newsgroups: comp.unix.wizards
Path: utzoo!henry
From: henry@utzoo.uucp (Henry Spencer)
Subject: Re: System V file systems
Message-ID: <1988Oct27.173247.2789@utzoo.uucp>
Organization: U of Toronto Zoology
References: <6413@daver.UUCP> <8332@alice.UUCP> <Oct.25.22.42.50.1988.1890@geneva.rutgers.edu>
Date: Thu, 27 Oct 88 17:32:47 GMT

In article <Oct.25.22.42.50.1988.1890@geneva.rutgers.edu> hedrick@geneva.rutgers.edu (Charles Hedrick) writes:
>(2) System V (at least SVr2, and I think also SVr3) uses a free list,
>which it does not keep in order, so an active file system fragments
>very soon.  The BSD file system is designed to avoid fragmentation.
>Of course this problem will not show if you do your tests right after
>creating the file system.

Or if you run your tests in a time-sharing environment, where the disk
heads are always on their way to somewhere else anyway.  If you read
the fine print, all the Berkeley performance tests were run single-user!!
We conjectured a long time ago that the only feature of the 4.2 filesystem
that matters much in a timesharing environment is the big block size; I
haven't yet seen any solid results (numbers, not anecdotes) that would
contradict this.
-- 
The dream *IS* alive...         |    Henry Spencer at U of Toronto Zoology
but not at NASA.                |uunet!attcan!utzoo!henry henry@zoo.toronto.edu
