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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