Creating a Temporary Cluster

JoshuaB · February 7, 2019, 09:48

I was wondering if anyone has experience in creating a system where say one has three computers that normally work separately, but on occasion they work as a cluster to solve larger problems.

The advantage for us would be that normally 3 people will have fairly powerful computers, but when required we can combine them together for a particularly large/long problem.

How difficult is this to do? I am using Ansys CFX.

Would I need to set up the computers to dual boot, once as an individual machine and on a cluster configuration? If possible, how long would it take to turnover from one configuration to the other.

Or am I just looking for trouble....

evcelica · February 11, 2019, 12:22

I do this at work with 5 computers and everything is seamless. All 5 users on the 5 machines can continue working normally while I and others can solve on the "cluster" of those 5 computers. No configuration switching needed, the machines can function as both 5 separate machines and a cluster simultaneously. I guess really it could be 5 clusters, as each machine can act as the head node and run the other 4 machines distributed, even at the same time.

Just follow the normal CFX distributed setup in the documentation.

I will expect followup questions on this standard CFX parallel process, it isn't simple the first time depending on you computer setup knowledge.

JoshuaB · February 12, 2019, 11:45

Thanks for the answer. Do you use Ethernet or infiniband for your clustering? I've heard with only a few computers infiniband doesn't really offer that much of an advantage, but if you have any experience I would be happy to hear it.

evcelica · February 12, 2019, 13:25

I use infiniband, since this cluster is also used for ANSYS mechanical FEA, which seems to need better node to node communication.

Though I ran one test using CFX and a large model using 1Gbps ethernet. Going from 1 machine to 2 machines showed almost perfectly linear speedup. (99.7%) this was using 4 cores on 1 machine vs 4 cores on each machine (8 total). So Yes, with just a few nodes, GigE shouldn't slow you down too much, if at all.

More nodes, or smaller models might not scale as well.

February 7, 2019, 09:48	Creating a Temporary Cluster	#1
JoshuaB New Member Joshua Brickel Join Date: Nov 2013 Posts: 26 Rep Power: 12	I was wondering if anyone has experience in creating a system where say one has three computers that normally work separately, but on occasion they work as a cluster to solve larger problems. The advantage for us would be that normally 3 people will have fairly powerful computers, but when required we can combine them together for a particularly large/long problem. How difficult is this to do? I am using Ansys CFX. Would I need to set up the computers to dual boot, once as an individual machine and on a cluster configuration? If possible, how long would it take to turnover from one configuration to the other. Or am I just looking for trouble....

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February 11, 2019, 12:22		#2
evcelica Senior Member Erik Join Date: Feb 2011 Location: Earth (Land portion) Posts: 1,167 Rep Power: 23	I do this at work with 5 computers and everything is seamless. All 5 users on the 5 machines can continue working normally while I and others can solve on the "cluster" of those 5 computers. No configuration switching needed, the machines can function as both 5 separate machines and a cluster simultaneously. I guess really it could be 5 clusters, as each machine can act as the head node and run the other 4 machines distributed, even at the same time. Just follow the normal CFX distributed setup in the documentation. I will expect followup questions on this standard CFX parallel process, it isn't simple the first time depending on you computer setup knowledge.

February 12, 2019, 11:45		#3
JoshuaB New Member Joshua Brickel Join Date: Nov 2013 Posts: 26 Rep Power: 12	Thanks for the answer. Do you use Ethernet or infiniband for your clustering? I've heard with only a few computers infiniband doesn't really offer that much of an advantage, but if you have any experience I would be happy to hear it.

February 12, 2019, 13:25		#4
evcelica Senior Member Erik Join Date: Feb 2011 Location: Earth (Land portion) Posts: 1,167 Rep Power: 23	I use infiniband, since this cluster is also used for ANSYS mechanical FEA, which seems to need better node to node communication. Though I ran one test using CFX and a large model using 1Gbps ethernet. Going from 1 machine to 2 machines showed almost perfectly linear speedup. (99.7%) this was using 4 cores on 1 machine vs 4 cores on each machine (8 total). So Yes, with just a few nodes, GigE shouldn't slow you down too much, if at all. More nodes, or smaller models might not scale as well.