Re: RFC: NFS trunking (multiple TCP connections for a mount

From: Rick Macklem <rmacklem_at_uoguelph.ca>
Date: Tue, 29 Jun 2021 20:22:31 +0000
Thanks everyone, for your comments. I now see (never used it
nor looked at it before) that lagg/lacp pins traffic for a TCP connection
to an interface (not infallibly for Peter).

I also now learned a little bit w.r.t. multiple queues for fast NICs.

Sounds like the "nconnect" option is worth implementing.

Thanks for your input, rick

________________________________________
From: Peter Eriksson <pen_at_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 “roundrobin” option in freebsd -  don’t do that unless you like out-of-order packets…)

Network equipment with laggs typically hash the IP streams over the lagg members 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/performance drops over our internal backbone network for certain combinations of odd/even IP addresses/port numbers when things pass certain SPB “routers” (which typically hash the streams over many “channels” between routers)… Fun fun. :-)

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

Just avoid the Linux NFS mounting deadlock issue with “down” servers please  :-)

- Peter
Received on Tue Jun 29 2021 - 20:22:31 UTC

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