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Date:      Wed, 9 Mar 2005 21:35:19 -0500
From:      David Schultz <das@FreeBSD.ORG>
To:        Mikhail Teterin <mi+mx@aldan.algebra.com>
Cc:        hackers@FreeBSD.ORG
Subject:   Re: the current status of nullfs, unionfs
Message-ID:  <20050310023518.GA11712@VARK.MIT.EDU>
In-Reply-To: <200503091838.06322.mi%2Bmx@aldan.algebra.com>
References:  <200503091838.06322.mi%2Bmx@aldan.algebra.com>

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On Wed, Mar 09, 2005, Mikhail Teterin wrote:
> Hello!
> 
> The respected manual contain dire warnings, but the Google search suggests, 
> the situation is not *that* gloomy.
> 
> For example, according to http://kerneltrap.org/node/652 , nullfs was used on 
> Bento-cluster two years ago in 2003.
> 
> Is anybody working on this file-systems? Any plans, rumours?

Nullfs works better than unionfs.  Unionfs worked well in 4.X.
Despite numerous minor bugs such as being unable to cope with
FIFOs, several people have reported using it quite successfully on
production systems.  However, unionfs no longer works quite as
well in 5.X or -CURRENT.  There are several reasons for this:

1. Nobody seems to have both the time and interest to maintain it.

2. Developers can't be expected to prevent regressions in
   something that's unsupported.

3. There are a couple of people who always respond to questions
   about unionfs with comments along the lines of:
   ``It's broken, so we won't help you.  Go away and don't tell
   us if you find any bugs.''

There's some pretty low-hanging fruit in terms of nits to fix.
See the PR database if you're interested in helping, and don't let
anyone scare you away.  ;-)

> What about the `union' option to regular mounts? Is that safe to use?

Last I checked, it was very broken, but I'm not sure.



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