If you use the --parallel argument at the CLI, it will use the gnu 'parallel' command (assuming you've installed it) and produce output like this:
seq 3 | parallel -j 0 -v "knife ec2 server create -S mray -i ~/.ssh/mray.pem -x ubuntu -G default -I ami-7000f019 -f m1.small -N webserver{} -r 'role[base],role[tc],role[users]'"
If you use the --parallel argument at the CLI, it will use the gnu 'parallel' command (assuming you've installed it) and produce output like this: seq 3 | parallel -j 0 -v "knife ec2 server create -S mray -i ~/.ssh/mray.pem -x ubuntu -G default -I ami-7000f019 -f m1.small -N webserver{} -r 'role[base],role[tc],role[users]'"