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    SubjectRe: Ext3 vs NTFS performance
    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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