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Date:      Sun, 24 Jan 1999 22:04:30 +0900
From:      "Daniel C. Sobral" <dcs@newsguy.com>
To:        Greg Lehey <grog@lemis.com>
Cc:        jm7996@devrycols.edu, Konrad Heuer <kheuer@gwdu60.gwdg.de>, freebsd-advocacy@FreeBSD.ORG
Subject:   Re: FreeBSD - A User's Point of View
Message-ID:  <36AB1A5E.35F73F4C@newsguy.com>
References:  <19990124171121.A36690@freebie.lemis.com> <Pine.BSF.4.05.9901240354030.215-100000@insomnia.local.net> <19990124201556.E36690@freebie.lemis.com>

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Greg Lehey wrote:
> 
> > The Linux filesystem, or ext2fs, if I'm not mistaken by default caches
> > writes to the disk.  If the machine should suddenly go down, power
> > failure, unexpected crash, etc..., this information doesn't make it back
> > to the disk.  I've known many a Linux user who has lost _entire_ file
> > systems due to this.
> 
> UFS does this too.

Ext2fs in Linux defaults to full-async: data and metadata. This is
much worse than ffs' default in FreeBSD, of metadata-sync +
data-async. FreeBSD's ffs can be configured as full sync or full
async, in addition to it's default behavior. AND, we now have
softupdates. :-) Ok, ok, it has licensing issues...

> I don't know if it's possible to turn it off in Linux.  You can't turn
> it off in UFS either.  In fact, the manner in which disk writes are
> cached is pretty central to FreeBSD's performance.

You can turn it off in Linux, though I don't know if they have a
"half-async" mode. As for FreeBSD, see above... :-)

> I think you've made my point.  This ``evil'' feature of ext2fs was
> probably borrowed, at least in concept, from BSD's UFS.

Nope, they default to full-async. That IS evil. If they don't have a
half-async, which gives much better resistance to crash, that's evil
too.

--
Daniel C. Sobral			(8-DCS)
dcs@newsguy.com

	If you sell your soul to the Devil and all you get is an MCSE from
it, you haven't gotten market rate.



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