From owner-freebsd-current  Sat Mar  7 16:33:05 1998
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From: Mikael Karpberg <karpen@ocean.campus.luth.se>
Message-Id: <199803080028.BAA03950@ocean.campus.luth.se>
Subject: Re: Okay, -current should be conditionally safe to use
In-Reply-To: <199803080012.TAA00282@dyson.iquest.net> from "John S. Dyson" at "Mar 7, 98 07:12:31 pm"
To: dyson@FreeBSD.ORG
Date: Sun, 8 Mar 1998 01:28:51 +0100 (CET)
Cc: current@FreeBSD.ORG
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According to John S. Dyson:
> Mikael Karpberg said:
> > 
> > Would tuning the NFS exported disk SoftUpdates do a significant difference?
> Yes.

> > For the moment I don't think we're ready to use the SoftUpdates code, since
> > we're using the machine for more then just play, but it might be an
> > interesting thing to try once it's more robust.
> > 
> It probably isn't a good idea to use softupdates in production yet.  However,
> another interesting thing to try is:
> 
> sysctl -w vfs.nfs.async=1
> 
> on the server.  This is better (safer) than softupdates, but you *can*
> have data lossage, due to writes not being committed to disk.  It is
> a good idea to have a UPS when using the above option.

We certainly don't have a UPS.
What exactly does turning on that sysctl mean? That we can get an
inconsistant state on the disk, like with mount option async, or that
writes are ACKed (or whatever you call it) directly, and then queued for
a normal write to the disk according to the disks mount options?
The latter would mean nothing except data loss at a crash, I guess, and
that doesn't seem so bad, since data written the second a crash or
power outage happens is still pretty much doomed.

And how is it better then SoftUpdates? Because it's not using beta-release
code, or are SoftUpdates a looser here for some other reason?

  /Mikael

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