A lot of effort has gone into cloud storage peformance benchmarking, both of swift and other cloud stacks and part of the result is a lot of confusion in the numbers, in large part because there is no standard. This is further complicated because some implementations are written in java, some in python and some in raw curl. Furthermore, the underlying libraries themselves can cause variances as they do not all use the same buffer sizes, enable/disable ssl-compression and probably other parameters as well.
I would like to talk about our benchmarking methodologies at HP as well as describe a tool suite I've developed that implements them and share some results of benchmarking our own OpenStack implementation. One thing I've discovered over previous months of testing is that both latency and cpu overhead can have a major impact on performance and those are captured as well, something most tools typically don't report.
The tools are written in python and use the OpenStack python-swiftclient library.