When beginning with PostMark, this disk benchmark that replicates a mail server workload had not experienced a huge fluctuation in performance among the Amazon EC2 instance types that offer a "high I/O performance" capability. These cloud computing instances were about 2.5x faster than the 32-bit m1.small and c1.medium instances with ratings of moderate I/O performance.
The m1.small EC2 instance was by far the slowest system of those tested (sans the t1.micro) for running GCC to compile the Apache web-server. The m2.2xlarge and m2.4xlarge instance types were effectively tied for being the fastest.
When it came to compiling PHP, the m2.4xlarge EC2 instance with twice as many EC2 Compute Units began separating itself from the m2.2xlarge type.