In the example above, the workload in question only needs a four-socket Xeon E5-4600 or Xeon E7-4800 in terms of the processing capacity, but the 48 to 64 memory sticks in this box do not offer enough main memory capacity, and moreover, the fat memory needed to build up terabytes of memory space are very expensive. So instead of buying an eight-socket box to get more memory slots, you get the four-socket box and put in the faster Xeon or Opteron processors you can afford. Then you buy a bunch of skinny server nodes with 24 memory sticks each, and you turn off the cores and leave on the memory controllers and memory in the boxes as well as the InfiniBand ports, and now the FDR links are effectively a backplane for an SMP based on the vSMP hypervisor.
If this sounds enticing, the good news is that there will soon be an easy way to kick the tires and give it a try. Morgan also writes that ScaleMP plans to roll out a variant of vSMP Foundation called Memory Expansion Free. As a free download without support, Memory Expansion Free will have one compute node and up to a total of eight nodes in a cluster and is also limited to four sockets of processing in a machine and 1TB of aggregate main memory across the server nodes in the cluster.
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