From: Dan Stromberg <strombrg@dcs.nac.uci.edu>
Subject: RE: NFS and tinygrams
Date: Thu, 21 Oct 2004 11:17:24 -0700
Sender: nfs-admin@lists.sourceforge.net
Message-ID: <1098382644.3601.183.camel@tesuji.nac.uci.edu>
References: <482A3FA0050D21419C269D13989C61130435E9E2@lavender-fe.eng.netapp.com>
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Cc: Dan Stromberg <strombrg@dcs.nac.uci.edu>,
        Linux NFS Mailing List <nfs@lists.sourceforge.net>
To: "Lever, Charles" <Charles.Lever@netapp.com>
In-Reply-To: <482A3FA0050D21419C269D13989C61130435E9E2@lavender-fe.eng.netapp.com>
Errors-To: nfs-admin@lists.sourceforge.net


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A tinygram is a small packet.

Many of the NFS packets I'm seeing are small - say about 200 or 300
bytes.  Then from time to time, there's a 7k packet, like I'd like to
see more of.

I don't think it's the TCP layer doing it, or we wouldn't be seeing our
7K packets from time to time.  TCP shouldn't fragment these, because
we've turned on "jumbo frames" and set our MTU's to 9000.  It about has
to be one or both NFS layers doing many small transfers I think.

Someone just told me that netapp servers can do intent-based NFS.  Do
you concur?

On Thu, 2004-10-21 at 10:47, Lever, Charles wrote:
> what's a "tinygram" ?
>=20
> do you mean the NFS write requests aren't all "wsize" bytes?  or do you
> mean the TCP layer is segmenting into small IP packets?  these are two
> separate layers, and do not interact.
>=20
> > -----Original Message-----
> > From: Dan Stromberg [mailto:strombrg@dcs.nac.uci.edu]=20
> > Sent: Thursday, October 21, 2004 1:05 PM
> > To: Linux NFS Mailing List
> > Cc: Dan Stromberg
> > Subject: [NFS] NFS and tinygrams
> >=20
> >=20
> >=20
> > We have a series of test transfers going, where we are=20
> > shuttling data from GFS->NFS V3 over UDP->NFS V3 over TCP->Lustre.
> >=20
> > On the NFS V3 over TCP link, we're seeing a lot of tinygrams,=20
> > despite having 8K NFS block sizes turned on, and jumbo=20
> > packets enabled (9000 byte MTU).
> >=20
> > The GFS machine runs Redhat 9, the first NFS server also runs=20
> > Redhat 9.=20
> > The machine copying from NFS to NFS is running AIX 5.1.  The=20
> > machine copying NFS to Lustre is running RHEL 3.
> >=20
> > I didn't check on the packet sizes of the other legs of the transfer.
> >=20
> > I've verified that we do have jumbo packets being used some=20
> > of the time, on that AIX 5.1 -> RHEL 3 hop.  However, we're=20
> > still getting a pretty large percentage of tinygrams.
> >=20
> > Is there any way of cutting down on the tinygrams, to more=20
> > effectively utilize our large MTU?  Is there perhaps any sort=20
> > of "intent based" packetizing in standard implementations of=20
> > NFS on Redhat 9, AIX 5.1, and/or RHEL 3?
> >=20
> > (Yes, we could short circuit the AIX 5.1 part of the=20
> > transfer, and that Would make things faster, but it Wouldn't=20
> > test what we need to test!)
> >=20
> > Thanks!
> >=20
> > --=20
> > Dan Stromberg DCS/NACS/UCI <strombrg@dcs.nac.uci.edu>
> >=20
> >=20
> >=20
> >=20
> > -------------------------------------------------------
> > This SF.net email is sponsored by: IT Product Guide on=20
> > ITManagersJournal Use IT products in your business? Tell us=20
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> > http://productguide.itmanagersjournal.com/guid> epromo.tmpl
> >=20
> > _______________________________________________
> >=20
> > NFS maillist  -  NFS@lists.sourceforge.net=20
> > https://lists.sourceforge.net/lists/listinfo/n> fs
> >=20
--=20
Dan Stromberg DCS/NACS/UCI <strombrg@dcs.nac.uci.edu>


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