Date: Wed, 2 May 2007 11:08:10 -0700
From: Jeremy Allison <jra@samba.org>
To: Theodore Tso <tytso@mit.edu>, Andrew Morton <akpm@linux-foundation.org>,
       "Cabot, Mason B" <mason.b.cabot@intel.com>,
       linux-kernel@vger.kernel.org, tridge@samba.com, jra@samba.org
Subject: Re: Ext3 vs NTFS performance
Message-ID: <20070502180810.GC28726@jeremy-laptop>
Reply-To: Jeremy Allison <jra@samba.org>
References: <B326D0531AF1BA48B4C1E9EBA239A050033DB3C1@scsmsx412.amr.corp.intel.com> <20070501142325.09c294bd.akpm@linux-foundation.org> <20070502161638.GB19442@thunk.org>
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On Wed, May 02, 2007 at 12:16:38PM -0400, Theodore Tso wrote:
> On Tue, May 01, 2007 at 02:23:25PM -0700, Andrew Morton wrote:
> > On Tue, 1 May 2007 13:43:18 -0700
> > "Cabot, Mason B" <mason.b.cabot@intel.com> 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.
> > 
> > Oh my gawd, what a stupid hack.  Now we know what the MS interoperability
> > lab has been working on.
> 
> I wonder if they patented this technique as well, as well as one of
> their dozen or so patents they are filing every day?  "A Method of
> Screwing Over Samba's Performance So that Windows Longhorn Can Compete
> On Performance" coming soon, to a patent database near you!  :-)
> 
> > > I've posted a brief paper on Intel's OSS website
> > > (http://softwarecommunity.intel.com/articles/eng/1259.htm). Please give
> > > it a read and let me know what you think. In particular, I'd like to
> > > arrive at the right place to fix this problem: is it in the filesystem,
> > > VFS, or Samba?
> 
> The right place is clearly Samba.  I can't think of any other program
> or filesystem protocol where writing a 1 byte write at 128k strides
> would be used to signal a desire to do preallocation.  In fact, it's
> hard to think of a worse way of doing things.

In fact they don't need to do this - there's an explicit CIFS
set file allocation call to pre-allocate size they could use.

There's a specific Samba VFS module that has XFS specific calls
to do this - vfs_prealloc. - but this won't work on ext3.

Jeremy.
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