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Subject: RE: Ext3 vs NTFS performance
Date: Fri, 4 May 2007 12:52:30 -0700
Message-ID: <B326D0531AF1BA48B4C1E9EBA239A0500343FD11@scsmsx412.amr.corp.intel.com>
In-Reply-To: <463B81D4.50401@cfl.rr.com>
Thread-Topic: Ext3 vs NTFS performance
Thread-Index: AceOfdu2BOeZb5guTMSFlac7bLRBHQABykaQ
From: "Cabot, Mason B" <mason.b.cabot@intel.com>
To: "Phillip Susi" <psusi@cfl.rr.com>
CC: <linux-kernel@vger.kernel.org>
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 1864
Lines: 45

> 
> Cabot, Mason B wrote:
> > I've been testing the NAS performance of ext3/Openfiler 2.2 against
> > NTFS/WinXP and have found that NTFS significantly 
> outperforms ext3 for
> > video workloads. The Windows CIFS client will attempt a poor-man's
> > pre-allocation of the file on the server by sending 1-byte writes at
> > 128K-byte strides, breaking block allocation on ext3 and leading to
> > fragmentation and poor performance. This will happen for many
> > applications (including iTunes) as the CIFS client issues these
> > pre-allocates under the application layer.
> 
> This is rather hard to believe so I think some more information is in 
> order.  Specifically, how do you know that it is the windows 
> kernel that 
> is issuing these writes and not the application?  Under what 
> application 
> access patterns does it do this?
> 
> This is just rather hard to believe seeing as how, iirc, the CIFS 
> protocol has commands to extend the file size properly rather 
> than with 
> this hack, and unless it is asked to by the application, the 
> cifs client 
> should not be trying to extend files.
>

Philip:

the best response I can offer is that we have traced the application's
file system accesses and seen no such one-byte writes occuring at that
level. They are generated somewhere below the application. Additionally,
while we have observed iTunes on Windows issuing these one-byte writes,
ethereal traces for iTunes on Mac OSX show no such behavior. Because of
these observations I think it is reasonable to conclude that the Windows
CIFS client is generating the one-byte writes.

thanks,
Mason
 
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