knife batch is a wonderful little plugin for executing commands a la knife ssh, but doing it in groups of n with a sleep between execution iterations.

gem install knife-batch

knife batch works exactly like knife ssh but with a couple of additional options. knife batch "role:cluster" "whoami" -B 10 -W 5 will execute whoami against 10 servers with a sleep of 5 seconds in between.

-B INTEGER defines how many servers at max will be batched. -W INTEGER defines the time to sleep in between executions.