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Date:      Thu, 1 Jul 2021 01:46:10 +0000
From:      Rick Macklem <rmacklem@uoguelph.ca>
To:        Peter Eriksson <pen@lysator.liu.se>
Cc:        freebsd-net <freebsd-net@freebsd.org>
Subject:   Re: RFC: NFS trunking (multiple TCP connections for a mount
Message-ID:  <YQXPR0101MB0968C4F4865ADA058CCEEA17DD009@YQXPR0101MB0968.CANPRD01.PROD.OUTLOOK.COM>
In-Reply-To: <362300CE-30DA-4552-A3E4-0F3DFE385B2A@lysator.liu.se>
References:  <YQXPR0101MB0968DC173855A82AAF45F08FDD039@YQXPR0101MB0968.CANPRD01.PROD.OUTLOOK.COM>,<362300CE-30DA-4552-A3E4-0F3DFE385B2A@lysator.liu.se>

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In case anyone is interested in testing and/or reviewing the patch,
it is at https://reviews.freebsd.org/D30970.

Only lightly tested at this point.

The NFS mount option is "nconnect=3D<N>", where 2<=3D N <=3D 16,
same as Linux. (I haven't done a man page patch yet.)

Thanks everyone, for your input, rick

________________________________________
From: Peter Eriksson <pen@lysator.liu.se>
Sent: Tuesday, June 29, 2021 5:11 AM
To: Rick Macklem
Cc: freebsd-net
Subject: Re: RFC: NFS trunking (multiple TCP connections for a mount

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> I don't understand how multiple TCP connections to the same
> server IP address will distribute the load across multiple network
> interfaces?
> I thought that lagg would have handled this?


A lagg typically keeps all data in a TCP stream on a specific lagg member (=
depending on how the lagg is set up, unless you select the =93roundrobin=94=
 option in freebsd -  don=92t do that unless you like out-of-order packets=
=85)

Network equipment with laggs typically hash the IP streams over the lagg me=
mbers based on MAC addresses (source&target), IP addresses (source&target) =
and port numbers.

(We have been diagnosing a fun problem locally where we see packet losses/p=
erformance drops over our internal backbone network for certain combination=
s of odd/even IP addresses/port numbers when things pass certain SPB =93rou=
ters=94 (which typically hash the streams over many =93channels=94 between =
routers)=85 Fun fun. :-)

I think the multiple NFS TCP streams could make for some nice performance i=
mprovements in certain cases. And it would be a more generalisation of havi=
ng multiple streams between two hosts - one-or-many over IPv4 and one-or-ma=
ny over IPv6 at the same time. Windows SMB has a similar feature.

Just avoid the Linux NFS mounting deadlock issue with =93down=94 servers pl=
ease  :-)

- Peter



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