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Date:      Thu, 15 Nov 2007 22:31:19 +0000 (GMT)
From:      Robert Watson <>
To:        Ivan Voras <>
Subject:   Re: FreeBSD 6.3 or FreeBSD 7.0
Message-ID:  <>
In-Reply-To: <fhf27d$f2a$>
References:  <> <fhf27d$f2a$>

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On Wed, 14 Nov 2007, Ivan Voras wrote:

> Marko Lerota wrote:
>> I see that 6.3 and 7.0 is comming. Now I'm using 6.2-RELEASE for my 
>> servers. To what should I upgrade? Which of them will be stable or 
>> production release?
> For low-loaded machines, 7.0 is stable enough even with all the new goodies 
> like ZFS, tmpfs, ULE - I have such a machine with almost 30 days uptime and 
> have done 24h+ stress testing on another machine before blessing it for 
> production - but I still wouldn't trust it for mission critical "heads will 
> roll" type of servers.
> If you can, try it on a spare or lightly loaded server, it's worth it.

It's probably worth pointing out three more things:

(1) Quite a bit of the work in 7.x has also had to do with improving
     stability; for example, I've spent a significant amount of time
     restructuring socket and netinet-layer code to reduce its vulnerability to
     TCP race conditions that earlier in the 6.x life cycle could lead to
     panics under high load with man TCP resets in flight.  These are papered
     over in 6.x in a less clean way because the changes to address the
     underlying source of the problems required significant changes I felt too
     aggressive to merge to 6.x.  So while 7.x comes with potentially
     destablizing new features, it also comes with a lot of cleanup relative to
     6.x that should have net stability benefits (at least in the long run).

(2) The  areas I would particularly stay away from in sensitive production
     servers are things like new file systems (ZFS), where the chances and
     consequences of failure may be greater.

(3) At least for now, a 7.x kernel works quite well with a 6.x user space, so
     if you want to try out the 7.x kernel to see how it runs for you, you can
     do that without disrupting your application installs.  You won't be able
     to use features like ZFS that depend on new userland tools and libraies,
     but you will be able to evaluate stability and performance for most base
     OS features.

7.0 is a .0 release, but I think it's also a really strong .0 release.  While 
I might hesitate to recommend ZFS in less experimental settings, I feel that 
the 7.0 kernel will prove to be one of our most stable, not to mention most 
performant, .0 releases to date.  I would encourage people to try it out and 
see how it goes for them, but as with all new releases, to do it with adequate 
caution and a fallback plan in the event you run into something that hasn't 
been found or addressed in testing to date.

Robert N M Watson
Computer Laboratory
University of Cambridge

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