foo.js

var docs = [];
for(var i = 0; i < 20000; i++) {
  docs.push({rnd: _rand(), t: "2013-06-23", N:7*i, A:1, V:0, n:"1234"});
}
docs.sort(function(a, b) {
  return a.rnd - b.rnd;
});

var t0 = Date.now();
db.foos.insert(docs);
db.getLastError();
var t1 = Date.now();

print(db.foos.find().count() + " documents inserted");
print("Took " + (t1 - t0) + "ms");

output.txt

MongoDB shell version: 2.4.5
connecting to: test
20000 documents inserted
Took 471ms