MongoDB's Write Lock Performance in 1.8 vs 2.0
Rick Copeland:
The global write lock in MongoDB will certainly not be mourned when it’s gone, but as I’ve shown here, its effect on MongoDB’s performance is significantly less than you might expect. In the case of non-faulting reads and writes (the working set fits in RAM), the write lock degrades performance only slightly as the number of writes increases, and in the presence of faulting writes, the lock-with-yield approach of 2.0 mitigates most of the performance impact of the occasional faulting write.

Original title and link: MongoDB’s Write Lock Performance in 1.8 vs 2.0 (©myNoSQL)
via: http://blog.pythonisito.com/2011/12/mongodbs-write-lock.html?m=1