Few Nonstop Fundamentals - III

IPM

IPM means Inter Process Message, is a type of message that is sent across a message bus to tie the processors of an MPP system together.

In the context of Nonstop, this is a message that is sent between any two processes within a given Nonstop Node or across an EXPAND network on Nonstop Nodes.

These messages are unsolicited requests that are sent to the $RECEIVE message queue of a specified process by another Nonstop Process.

On Nonstop X, InfiniBand is the bus fabric.

RDMA

RDMA means Remote Direct Memory Access, is a capability specific to ServerNet and Infiniband architectures where by the memory of a given CPU can be directly referenced by a process in another CPU without the CPU that owns the memory being involved in the I/O operation.

There is no context Switching, Interrupt or Trap Handling needed to service the I/O.

Everything happens in user mode during the process execution time slice for maximum efficiency.