[gpfsug-discuss] connected v. datagram mode

[Jan-Frode Myklebust]

I also don't know much about this, but the ESS quick deployment guide is
quite clear on the we should use connected mode for IPoIB:

--------------
Note: If using bonded IP over IB, do the following: Ensure that the
CONNECTED_MODE=yes statement exists in the corresponding slave-bond
interface scripts located in /etc/sysconfig/network-scripts directory of
the management server and I/O server nodes. These scripts are created as
part of the IP over IB bond creation. An example of the slave-bond
interface with the modification is shown below.
---------------


-jf
fre. 12. mai 2017 kl. 16.48 skrev Aaron Knister <aaron.s.knister at nasa.gov>:

> For what it's worth we've seen *significantly* better performance of
> streaming benchmarks of IPoIB with connected mode vs datagram mode on IB.
>
> -Aaron
>
> On 5/12/17 10:43 AM, Jonathon A Anderson wrote:
> > This won’t tell you which to use; but datagram mode and connected mode
> in IB is roughly analogous to UDB vs TCP in IP. One is “unreliable” in that
> there’s no checking/retry built into the protocol; the other is “reliable”
> and detects whether data is received completely and in the correct order.
> >
> > The last advice I heard for traditional IB was that the overhead of
> connected mode isn’t worth it, particularly if you’re using IPoIB (where
> you’re likely to be using TCP anyway). That said, on our OPA network we’re
> seeing the opposite advice; so I, to, am often unsure what the most correct
> configuration would be for any given fabric.
> >
> > ~jonathon
> >
> >
> > On 5/12/17, 4:42 AM, "gpfsug-discuss-bounces at spectrumscale.org on
> behalf of Damir Krstic" <gpfsug-discuss-bounces at spectrumscale.org on
> behalf of damir.krstic at gmail.com> wrote:
> >
> >     I never fully understood the difference between connected v.
> datagram mode beside the obvious packet size difference. Our NSD servers
> (ESS GL6 nodes) are installed with RedHat 7 and are in connected mode. Our
> 700+ clients are running RH6 and
> >      are in datagram mode.
> >
> >
> >     In a month we are upgrading our cluster to RedHat 7 and are debating
> whether to leave the compute nodes in datagram mode or whether to switch
> them to connected mode.
> >     What is is the right thing to do?
> >
> >
> >     Thanks in advance.
> >     Damir
> >
> >
> >
> > _______________________________________________
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> > gpfsug-discuss at spectrumscale.org
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> >
>
> --
> Aaron Knister
> NASA Center for Climate Simulation (Code 606.2)
> Goddard Space Flight Center
> (301) 286-2776
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>
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