Hi Jeff,
Thanks a lot for your answer, It really makes sense.
Do you know where can I find more information about the *process launch on
remote nodes* of MPI and all the alternatives I have?
Thanks and regards.
From: users on behalf of Jeff Squyres
(jsquyres) via users
Sent: Wednesday, December 19, 2018 7:18:23 PM
To: Open MPI User's List
Cc: Jeff Squyres (jsquyres)
Subject: Re: [OMPI users] It's possible to get mpi working without ssh?
On Dec 19, 2018, at 11:42 AM, Daniel Edreira wrote:
>
> Does anyone know if there's a possibility to configure a cluster of nodes to
> communicate with each other with mpirun without using SSH?
>
> Someone is asking me about making a cluster with Infiniband that does not use
> SSH to communicate using OpenMPI.
I'm not entirely clear what you're asking. You mention both "ssh" and
"communication" -- they're kinda different things.
Communication: Over an InfiniBand cluster, we'd recommend that you use the UCX
library for Open MPI to communicate over IB. I.e., when your MPI application
invokes API calls like MPI_Send() and MPI_Recv(), they'll use the UCX library
underneath and utilize native IB-style communication (i.e., they're not using
the POSIX sockets API -- they're using the native UCX/verbs APIs for RDMA OS
bypass and offload, ...etc.).
Ssh: ssh is not used for *communication*, per se; it's used for *starting Linux
processes on remote nodes. Open MPI can use SSH to start processes on remote
nodes, but it can also use other mechanisms (e.g., if you have a resource
manager such as SLURM, Open MPI can use SLURM's native remote process launching
mechanism instead of SSH).
These two things are orthogonal to each other: you can use whatever
*communication* mechanism you want for MPI APIs (e.g., the POSIX sockets API or
the UCX library or ...several other APIs...), and use whatever *process launch*
mechanism you want (e.g., SSH or SLURM's native remote process launch or
...several others...). Put simply: the choice of MPI communication layer does
not imply anything about the remote process launch mechanism, and vice versa.
Make sense?
--
Jeff Squyres
jsquy...@cisco.com
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