Message-ID: <4678B46F.7070506@zytor.com>
Date: Tue, 19 Jun 2007 22:00:31 -0700
From: "H. Peter Anvin" <hpa@zytor.com>
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To: Trond Myklebust <trond.myklebust@fys.uio.no>
CC: Bryan Henderson <hbryan@us.ibm.com>,
       Lennart Sorensen <lsorense@csclub.uwaterloo.ca>,
       akpm@linux-foundation.org, alan <alan@clueserver.org>,
       Chris Snook <csnook@redhat.com>,
       Jack Stone <jack@hawkeye.stone.uk.eu.org>,
       linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
       viro@zeniv.linux.org.uk
Subject: Re: Versioning file system
References: <OF35839FC7.229AE944-ON882572FF.007F2DF8-882572FF.00819E1C@us.ibm.com> <1182299263.6504.8.camel@heimdal.trondhjem.org>
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Trond Myklebust wrote:
>>
>> I assume NetApp flags the directory specially so that a POSIX directory 
>> read doesn't get it.  I've seen that done elsewhere.
> 
> No. The directory is quite visible with a standard 'ls -a'. Instead,
> they simply mark it as a separate volume/filesystem: i.e. the fsid
> differs when you call stat(). The whole thing ends up acting rather like
> our bind mounts.
> It means that you avoid all those nasty user issues where people try to
> hard link to/from .snapshot directories, rename files across snapshot
> boundaries, etc.
> 

Last I used a Netapp, it was configurable, I believe; I seem to also
vaguely remember that one could configure it so that it only was
accessible as part of a mount string rather than as part of an
already-mounted filesystem.  Of course, this was a long time ago.

	-hpa
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