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From: louie@sayshell.umd.edu (Louis A. Mamakos)
Newsgroups: comp.sys.next
Subject: Re: disks filling up...
Message-ID: <1990Jun13.121953.4119@haven.umd.edu>
Date: 13 Jun 90 12:19:53 GMT
References: <1990Jun6.165425.18146@agate.berkeley.edu> <42891@brunix.UUCP>
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In article <42891@brunix.UUCP> rca@cs.brown.edu (Ronald C.F. Antony) writes:
>to avoid that a completely filled up disk looses it's content, the
>disk has 110% or so capacity (of course just a pseudo percentage...)
>and noone except root can write anything as soon as the 100% out of
>110% are reached...

This is, of course, nonsense.  The reason that that the disk fills at 90% (or
95% or whatever) is a performance issue related to the fact that the NeXT is
using the Berkeley Fast File System.  If you look at the man page for tunefs(8)
you'll see:

- - - - - - - - -

TUNEFS(8)	    UNIX Programmer's Manual		TUNEFS(8)



NAME
     tunefs - tune up an existing file system

SYNOPSIS
     /usr/etc/tunefs tuneup-options special|filesys

DESCRIPTION
     Tunefs is designed to change the dynamic parameters of a
     file system which affect the layout policies.  The parame-
     ters which are to be changed are indicated by the flags
     given below:

	.
	.
	.

     -m minfree
	  This value specifies the percentage of space held back
	  from normal users; the minimum free space threshold.
	  The default value used is 10%.  This value can be set
	  to zero, however up to a factor of three in throughput
	  will be lost over the performance obtained at a 10%
	  threshold.  Note that if the value is raised above the
	  current usage level, users will be unable to allocate
	  files until enough files have been deleted to get under
	  the higher threshold.
	.
	.
	.

- - - - - - - - -

If you wanted to suffer lower performance thruput to the file system, you
can tweak the minfree parameter to use more of the "available" disk space.
You might also look at the man page for fs(5) for more gory details.

Note that "root" can allocate every block on the disk, so that you can have
a file system which is 110% full.

And don't forget and always remember:

     You can tune a file system, but you can't tune a fish.



louie