Re: how to preserve QP over HA events for librdmacm applications

On 09/20/2012 01:10 PM, Hefty, Sean wrote:

quoted

What if you say pre-created a second (fail over) QP for HA purposes all
under the covers of a single socket? And both QPs were connected before
the failure. Not sure if that would work with the same CM id though. If
not, we will need to rdma_connect() the second QP after failure.

CM IDs are not shared across devices, and can't be reused for different QPs until the first connection has been torn down and gone through timewait.  For IB, you probably want path migration capabilities.

Fair enough, I understand one needs to use a different CM id. For the IB 
case I was thinking of avoiding APM (since that is limited to a device 
-isn't that so?).

Anything more generic should really be handled by the application.  Migrating a connection between devices also requires using different CQs, PDs, MRs, etc.

Is PD device specific? Couldn't one reuse the same CQs and MRs, even 
though the QP is different? Of course only one QP would be active at any 
time.

Thanks
Pradeep

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