Comparing Plura to Amazon’s EC2 for High Performance Computing

Amazon has recently come out of beta with their EC2 service, as noted by several sources:

EC2 has been extremely successful since its launch.

I’d like to do a quick comparison between Plura and EC2 for high performance computing.  (Note: All EC2 information was taken from Amazon’s website.)

Compute Performance

EC2 High-CPU Medium Instance nodes provide 1.7 GB of memory, 350 GB of instance storage and local network accesses between EC2 nodes at no charge.  Plura nodes vary in memory and size and we never use the disk.  Plura applications can request nodes with a minimum memory size if necessary.  Also, Plura nodes are not connected.  Each node knows only about its own tasks and can’t share with others.  This lends Plura to what’s called embarrassingly parallel applications of HPC.  That said, we have techniques for making some very difficult algorithms embarrassingly parallel.

Plura has a significant advantage over EC2 in terms of amount of available computing power.  Right now, the maximum # of nodes a customer can have on EC2 is about 1,000 to 3,000 nodes.  On Plura, customers have access to the entire node pool, which is currently over 50,000 nodes.  This gives Plura users significantly more compute power.


Each EC2 High-CPU Medium instance costs $0.20/hour.  This is equivalent to paying $1752/year for a  5-6 GHz CPU.  Plura charges approximately $100/year for a 2 GHz CPU (the average speed of nodes on our network).

The “conversion factor” between Plura nodes and EC2 nodes would be 2.5 Plura nodes = 1 EC2 High-CPU Medium Instance.  So Plura charges $250/year for the equivalent of 1 EC2 node, while Amazon charges $1752/year.

Side note: If you need to use EC2 nodes with Internet bandwidth, the $/year goes by $1000s/year for each node.  For now, Plura builds this in for free.


For HPC applications that need a lot of inter-node communication, EC2 will probably suit your needs better even at a higher cost.  However, if your application is suitable for Plura, you can save 7X on your compute costs.  If you need the equivalent of 1000 5 GHz nodes for a year, Plura will save you over $1.5 million ($250K vs $1.75M).


4 Responses to “Comparing Plura to Amazon’s EC2 for High Performance Computing”

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  2. 2 Bill Bryce March 11, 2009 at 2:38 pm

    It seems to me that the conclusions in this post don’t match up with reality.

    1) Using EC2 for ‘inter-node’ parallel jobs doesn’t make sense. It may make sense for non-HPC workloads but for real tightly coupled HPC it is bad, definitely not worth the money.

    2) Embarrassingly Parallel applications are common but there are also alot of true parallel apps used every day and these won’t work on Plura.

    3) EC2 allows a user to ‘take their existing local software stack and move the whole stack + applications into EC2 without any changes’ just run your app. You can’t do this with Plura.

    Finally – this blog entry was pretty lonely – not much response so I thought I would post some.


  3. 3 Brad Wilson March 11, 2009 at 2:58 pm

    Hi Bill,

    Thanks for the comment. I agree with all of your points. EC2 doesn’t really make much sense for tightly-coupled HPC jobs, but it definitely works better than Plura for those apps. Whether or not it is economical for those uses probably depends on the specific application and how much the user needs to run it.

    The applications that benefit most from Plura are in need of huge CPU counts and don’t mind porting their code to our safe java API to get access to the higher node count. This post was really intended to compare the costs of the two services for the subset of applications which make sense for Plura.


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