[Lustre-discuss] Multiple interfaces in LNet

Danny Sternkopf dsternkopf at hpce.nec.com
Mon Oct 13 08:29:14 PDT 2008


I learn about LNet and I also have read one of the recent post with
subject 'Adding IB to tcp only cluster'.

Interesting is how to use multiple interfaces on the same server in
Lustre/LNet. My understanding is that TCP(ksocklnd) can manage multiple
physical interfaces as one LNet interface with one unique NID. Is that
still correct and recommended to use? Or is it better to setup Ethernet
bonding(under Linux) and bind that bonding interface to LNet?

Beside of TCP it is only possible to use multiple interfaces on the same
node with o2ib, right? With ko2iblnd one can setup several Lustre
networks for each IB interface. In fact you must setup several Lustre
networks otherwise only the 1st IB interface is used, correct?

It is not clear for me how MGS, MDS, OSS and Client choose a NID for
communication. I mean I know that LNet choose the best one, but who
provides the list with all available NIDs for a server? Or does it work
somehow different?

I'am aware of 'lctl list_nids' and 'lctl which_nid <list of nids>'. That
 is fine. I would like to know what a Lustre server or a client does.

Furthermore I don't get the MGS target information kept in MDT and OST
devices. For what and how is it used? What happens during mount of MDT
or OST and who talks to each other and how?

I'am looking forward to get some better understanding. Thank you and
Best regards,

Danny Sternkopf http://www.nec.de/hpc       dsternkopf at hpce.nec.com
HPCE Division  Germany phone: +49-711-68770-35 fax: +49-711-6877145
NEC Deutschland GmbH, Hansaallee 101, 40549 Düsseldorf
Geschäftsführer Yuya Momose
Handelsregister Düsseldorf HRB 57941; VAT ID DE129424743

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