title: Why does MongoDB perform better with multi-threaded client compared to a single threaded client?
body: <p>We recently benchmarked Oracle 10g and MongoDB with YCSB ( <a href="https://github.com/brianfrankcooper/YCSB/wiki" rel="nofollow">https://github.com/brianfrankcooper/YCSB/wiki</a> ), when we tried to increase the number of threads for 1,000,000 datasets, Oracle's performance remained constant after 4 threads however MongoDB kept on  performing better and better till 8 threads and after that only reads were better, writes and updates (operations/sec) remained constant. </p>
  
  <p>We ran this benchmark on 2 CPU Xeon quad core (total 8 cores) + 8 GB RAM on LAN.</p>
  
  <p>What we observed was that MongoDB performed better with multi-threaded client comparing to single-threaded client, my question is: when MongoDB can perform better with more load why can't it do the same with less load (say just a couple of threads) by utilizing the multiple cores?</p>