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From: Neil Brown <neilb@cse.unsw.edu.au>
To: Lincoln Dale <ltd@cisco.com>
Date: Wed, 12 Jan 2005 09:02:35 +1100
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Cc: Phy Prabab <phyprabab@yahoo.com>, linux-kernel@vger.kernel.org
Subject: Re: Linux NFS vs NetApp
In-Reply-To: message from Lincoln Dale on Tuesday January 11
References: <message from Phy Prabab on Monday January 10>
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On Tuesday January 11, ltd@cisco.com wrote:
> At 08:54 PM 11/01/2005, Neil Brown wrote:
> >If you want to come anything close to comparable with a Netapp, get a
> >few hundred Megabytes of NVRAM (e.g. www.umem.com), and configure it
> >as an external journal for your filesystem (I know this can be done
> >for ext3, I don't know about other filesystems).  Then make sure your
> >filesystem journals all data, not just metadata (data=journal option
> >to ext3).
> 
> NetApp's WAFL only journals metadata in NVRAM ...
> (one of the primary reasons its called WAFL is that the data-write only 
> happens once..).
> 

That may be, though it doesn't fit with my (admittedly limitted)
understanding of WAFL.

However Linux NFS definitely runs faster over ext3 if data=journal is
selected.

NeilBrown