In my understanding, the standard is mainly for the hardware and misc stuff only. For example, mellanox and qlogic infiniband can use the same cables and switches. Iirc, they can use the same subnet manager and communicate via IPoIB.
When performance matters, mellanox use ib verbs, and qlogic uses PSM library. I am not sure what you mean by "ompi prefers PSM over other IB" assuming qlogic can work with IB verbs, then yes, PSM is faster for qlogic, so ompi will prefer PSM. Mellanox infiniband cannot use PSM so ompi use IB verbs. Note mellanox also provides optimized proprietary libraries (hcoll, mxm, ...) that can be used for enhanced performances. Fwiw and iirc, Intel bought the infiniband assets from Qlogic a few years ago. Cheers, Gilles On Saturday, March 12, 2016, dpchoudh . <dpcho...@gmail.com> wrote: > Hello all > > I have a question, that I do realize, is somewhat off topic to this list. > But I do not know who to approach for an answer. Hopefully the community > here will help me out. > > I know that Infiniband is a 'standard' interface (standardized by IETF? > IEEE? or some similar body), much like Ethernet. > > However, I do see that they come in different 'flavors', (and have > different feature set?) such as Qlogic PSM or Mellanox ConnectX, that have > *user space* "drivers" and even OpenMPI treats them differently (preferring > Qlogic PSM over other IB, as a default behavior). > > For someone very new to the Infiniband world, what are the differences? > How can they be different and yet confirm to the (supposed) standard? > > Any pointer to appropriate literature is appreciated. > > Thanks in advance > Durga > > Life is complex. It has real and imaginary parts. >
