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The maximum read throughput I was able to observe from a single client machine was only ~29 512Byte-read operations per second using 8 processes (each of 4 Java threads). I don't understand the behavior of the client library (which seems to spawn about 11 threads of its own), so I can't really explain this.
1 client machine: 5.6Kops/s
2 client machines: 10.4Kops/s
3 client machies: 15.7Kops/s
4 client machines: 20.0Kops/s