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Date:      Wed, 30 Jan 2002 14:14:02 -0500
From:      Brian T.Schellenberger <bts@babbleon.org>
To:        Doug Poland <doug@polands.org>, Espen Tagestad <espen@modula.no>
Cc:        questions@FreeBSD.ORG
Subject:   Re: Softupdates ( why not to use on / fs )
Message-ID:  <20020130191402.D84744078@i8k.babbleon.org>
In-Reply-To: <20020130095919.B26823@polands.org>
References:  <3C593C4A@epostleser.online.no> <20020130124756.A15728@modula.no> <20020130095919.B26823@polands.org>

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Better lesson to have learned:

a. Turn off write caching.  This should be off by default IMHO.
The default sacrifices out-of-the-box safety for out-of-the box performance 
numbers vis-a-vis Linux.

If this happened to you and you already had write caching off already, then 
*that* would be quite interesting, and both the members of hte list and the 
author of the softupdates code would probably want to know about it.

Only a file which is just being written should be at risk from turning on 
soft updates without write caching.


On Wednesday 30 January 2002 10:59 am, Doug Poland wrote:
> On Wed, Jan 30, 2002 at 12:47:56PM +0100, Espen Tagestad wrote:
> > On Wed, Jan 30, 2002 at 12:34:11PM +0100, Christer Gundersen wrote:
> > > As i read the RELEASE NOTES, i see that SOFTUPDATES will be activated
> > > by default under install. but it also says that it will not enable
> > > SOFTUPDATES on the root ( / ) fs . why? is that bad?
> >
> > Because with SoftUpdates read/write operations often delay, sometimes
> > up to 30 seconds before it's done. Then, if a machine crash occurs it
> > may lead to a larger loss of data. That can cause unrecoverable damage
> > to your system.
>
> I can attest to that.  Last week I changed my /etc/fstab.  Immediatley
> after exiting vi, I mounted a floppy with a FAT filesystem with the
> intention of saving this important system file.  I forgot to disable
> the write-protect tab on the floppy and simply popped the floppy out
> of the drive, switched the tab,  and put it back in.  When I did an
> ls /dev/fd0 my system hung.  I reset the machine, the / partition
> had errors that fsck fixed.  Unfortunately, /etc/fstab was gone. Ouch.
> It took me two hours to get my box up and running again.
>
> Lessons learned:
> 1. turn off softupdates on /
> 2. be VERY careful mounting/unmounting removable media
> 3. before disaster strikes...
> 4. have a fixit floppy/cd before #3
> 5. print portion of handbook dealing with Emergency Restore Procedures
>
> HTH,

-- 
Brian T. Schellenberger . . . . . . .   bts@wnt.sas.com (work)
Brian, the man from Babble-On . . . .   bts@babbleon.org (personal)
                                ME -->  http://www.babbleon.org
http://www.eff.org   <-- GOOD GUYS -->  http://www.programming-freedom.org 

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