Setup. Keeper in goal. A server 10 metres out, level with each post.
How it runs. The keeper touches one post, side-steps across the goal, sets in line with the far server and saves a low shot. Straight back across to save from the other server. Six saves without stopping, then rotate. This is a match-speed drill: the next shot comes as soon as the keeper could reasonably be there.
Make it harder. Servers hit it first time as the keeper arrives. Then the second save has to be held, or the first server follows in on the rebound.
With 4 keepers. Keeper, two servers, one resting.