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Date:      Tue, 11 Dec 2001 15:40:37 -0700
From:      Warner Losh <imp@harmony.village.org>
To:        Greg Lehey <grog@FreeBSD.org>
Cc:        Terry Lambert <tlambert2@mindspring.com>, Nik Clayton <nik@FreeBSD.org>, Mike Smith <msmith@FreeBSD.org>, arch@FreeBSD.org, Marko Zec <zec@tel.fer.hr>, "Louis A. Mamakos" <louie@TransSys.COM>, Matthew Dillon <dillon@apollo.backplane.com>, Sheldon Hearn <sheldonh@starjuice.net>, freebsd-arch@FreeBSD.org
Subject:   Re: Getting rid of /usr file system (was: Using a larger block size on large filesystems) 
Message-ID:  <200112112240.fBBMebM31038@harmony.village.org>
In-Reply-To: Your message of "Wed, 12 Dec 2001 09:06:10 %2B1030." <20011212090610.D67986@monorchid.lemis.com> 
References:  <20011212090610.D67986@monorchid.lemis.com>  <20011210124458.B63585@monorchid.lemis.com> <20011208102658.B11428@dragon.nuxi.com> <200112082050.fB8Ko1T01347@mass.dis.org> <20011209164606.C83634@monorchid.lemis.com> <20011209104437.A69671@clan.nothing-going-on.org> <3C141A26.9D8BC688@mindspring.com> <200112110946.fBB9kMM26143@harmony.village.org> 

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In message <20011212090610.D67986@monorchid.lemis.com> Greg Lehey writes:
: On Tuesday, 11 December 2001 at  2:46:22 -0700, Warner Losh wrote:
: > In message <20011210124458.B63585@monorchid.lemis.com> Greg Lehey writes:
: > : Well, I'm not forgetting this, I didn't know it.  But it seems to make
: > : sense.  This was one of the things I mentioned earlier.
: >
: > I have had systems that have separate / and /usr, and others that have
: > one big /.  I don't mind so much that / and /usr are on the same
: > partition by default, but I don't want to see us go to one big '/'.
: > That does cause more problems than it solves (and makes it impossible
: > to do fastish boots by kicking the fsck into the back ground).
: > However, I've had occasion to have systems where / and /usr need to be
: > separate partitions, so as long as we don't require them to be on the
: > same partition, I'd say go for it.
: >
: > I suspect, however, that we'll find that crash recovery really is a
: > big factor since /usr does get written to on every man command that
: > generates a new man page...
: 
: That's pretty seldom.
: 
:  $ find /usr/share/man/cat* -type f | wc -l
:     3277
:  $uname -v
:  FreeBSD 5.0-CURRENT #0: Sat Sep 30 17:31:17 CST 2000     grog@wantadilla.lemis.com:/src/FreeBSD/WANTADILLA/src/sys/compile/WANTADILLA 
: 
: That's about 7.5 man pages per day.  This is on my main machine, and I
: suspect I use man pages more than most.
: 
: More to the point, how many broken /usr file systems have you *ever*
: had with FreeBSD?

Maybe 5.  I've rarely had one when / wasn't also broken. :-)

However, the argument for /usr is more than just that it is for crash
recovery.  I'd have fewer if /usr was mounted read only (which it
can't be for the man page issue, and other problems).  We mount / read
only on our embedded systems and combine / and /usr onto one partition
and like everything dynamic.  We also mount /var on MFS and have a
read/write /mod for things that change (but that can be recovered by
some means, should we need to newfs things).

The argument is that if / is small, the chances of it being corrupt
are smaller and the risk is lower of using it as an unchecked file
system.

Warner

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