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Date:      Fri, 27 May 2005 19:25:44 +1000
From:      Peter Jeremy <PeterJeremy@optushome.com.au>
To:        Scott Long <scottl@samsco.org>
Cc:        FreeBSD Current <freebsd-current@freebsd.org>
Subject:   Re: Disable read/write caching to disk?
Message-ID:  <20050527092544.GB18696@cirb503493.alcatel.com.au>
In-Reply-To: <42969C1B.5010301@samsco.org>
References:  <42960ACB.7090801@cs.tu-berlin.de> <42960CFE.4060307@centtech.com> <42960F8F.2050109@samsco.org> <42961195.30608@centtech.com> <429613FB.80100@samsco.org> <42968AD4.3020603@centtech.com> <A70C5E4F-D9F9-4756-8AC2-591462E338DE@shire.net> <4296997C.9030700@samsco.org> <20050526235852.M54386@lexi.siliconlandmark.com> <42969C1B.5010301@samsco.org>

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On Thu, 2005-May-26 22:03:39 -0600, Scott Long wrote:
>A few people have suggested modifying UFS to fill this role.  It probably
>is just as much work as porting GFS, if not more, since UFS/FFS is 
>closely tied to the buffer cache and block layers on BSD, and divorcing
>probably would be quite difficult.

It's probably worth noting that (AFAIK) none of the commercial vendors
have managed to build a multi-master shared UFS filesystem.  This
suggests that the effort is considerable.

Solaris clustering routes all I/O to a shared filesystem to a single
'master' node, which is responsible for all physical I/O to the disk.
This would significantly simplify cache coherency management.

Tru64 clustering only really supports AdvFS.  Limited UFS support was
added in 5.1B - all the cluster members can mount a UFS filesystem but
only one can have a R/W mount and all I/O is routed through a single
"master" node.

-- 
Peter Jeremy



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