CPU is a major bottleneck for Rackspace Cloud. All instance sizes get the same 4 cores and about the same compute resources. CPU performance is roughly the same

CPU is a major bottleneck for Rackspace Cloud. All instance sizes get the same 4 cores and about the same compute resources. CPU performance is roughly the same on a 1GB cloud server as an 8GB cloud server, you are just paying for more memory. Rackspace also uses ONLY Opteron 2374 2.20 GHz processors. EC2 on the other hand offers linear CPU performance improvement on larger sized instances. EC2 also uses a heterogenous hardware ranging from Opteron 2218 or Xeon E5430 for m1 instances; Xeon E5410 for c1 instances; Xeon X5550 for m2 instances and Xeon X5570 (hyper-threaded to 16 cores) for the cluster compute instances. EBS on the cluster instance is also much faster than local disk IO in the Rackspace Cloud based on testing I've done (due to non-blocking 10G network). Here are a couple of references for this: http://blog.cloudharmony.com/2010/05/what-is-ecu-cpu-benchmarking-in-cloud.html http://blog.cloudharmony.com/2010/05/what-is-ecu-cpu-benchma... http://blog.cloudharmony.com/2010/06/disk-io-benchmarking-in-cloud.html http://blog.cloudharmony.com/2010/06/disk-io-benchmarking-in...