From owner-freebsd-performance@FreeBSD.ORG  Thu Jan 31 01:49:18 2008
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To: "Steven Hartland" <killing@multiplay.co.uk>
In-reply-to: Your message of "Thu, 31 Jan 2008 01:04:00 GMT."
	<013201c863a5$2a91a1c0$b6db87d4@multiplay.co.uk> 
Date: Wed, 30 Jan 2008 17:47:04 +0000
From: Dieter <freebsd@sopwith.solgatos.com>
Cc: freebsd-performance@freebsd.org, freebsd-stable@freebsd.org
Subject: Re: newfs locks entire machine for 20seconds 
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> > What *exactly* do you mean by
> > 
> >> machine still locks up with no activity for anywhere from 20 to 30 seconds.
> > 
> > Is there disk activity? (e.g. activity light(s) flashing if you have them)
> 
> Cant tell if there is disk activity its in a DC miles away ;)
> 
> > Does top continue to update the screen during the 20-30 seconds?
> >
> > I'm thinking that newfs has queued up a bunch of disk i/o, and other
> > disk i/o gets locked out, but activities that don't require any disk i/o
> > (like top, once it is up and running) could continue.  Is that what is
> > happening?
> 
> No all sessions totally freeze. I have top set to 1 second refreshes and
> the clock literally stops and then 20-30 seconds later continues.

Wow!

> All sessions are via ssh not X if that's of interest.
> 
> I could understand if IO to disk for other processes became slow but
> everything including things like top just stop which is quite odd and
> concerning.

Ok, new idea.  Your disk activity is via the network, and your sessions
are via the network.  Could it be that something network related is saturated?