mongoDB Configuration File Tuning

For those of us who are regular to MySQL, its configuration file (my.cnf) and the many options in it (some may say too many), mongoDB seems to be the simple.
With only few dozens of parameters in the configuration file (mongo.conf) and a dozen that are actually related to performance tuning, it may be a relatively short task to tune a mongoDB configuration file. Probably some of us will pay for that in production...

NOTE: this post does not refer the Sharding configuration.

What Can be Done?

Number of Connections
Like many other products (Apache httpd, MySQL...) the number of user connections can affect performance. mongoDB supports that using maxConns = N. Numbers can reach 20,000, but you should adjust it to your own server resources.

Write to Disk
Disk writing is usually a bottleneck in database systems. Therefore, wrtie to disk frequency and initial storage allocation can highly efhttp://stackoverflow.com/questions/8331099/what-is-the-javascript-engine-that-runs-mongodb-shellfect your system performance. Yet notice that delaying disk writing can effect your system recovery (many of you probably familiar with it from MySQL).
You should notice the following two options:

1. Delay journal (database log) write to disk using journalCommitInterval = 300. This parameter supports intervals between 2ms (slowest but safest for recovery) and 300ms (fastest but prone to recovery options). The default os 100ms, but you may increase it to 300ms to save resources.
2. Preallicate space at mongoDB startup by keeping noprealloc = false.

Disable Services
mongoDB provides many supporting services. Disabling some of them (if you do not use them), may help you save some CPU cycles:

1. BSON validation using objcheck = false.
2. HTTP Interface using nohttpinterface = true. The mongoDB HTTP interface exposes the database statistics and enables simple REST queries through port 28017.
3. Scripting Engine using noscripting = true. mongoDB is using SpiderMonkey JavaScript scripting engine to enable interactive shell. Somehow, I have a feeling that you are not going to disable it.
4. REST service using rest = false. See in the HTTP interface.
5. Profiling service (inc. slow queries logging) using profile = 0.

Bottom Line

mongoDB is a simple, yet very effective tool to solve many business needs. Doing some tuning will help you avoid issues during peak times.

Keep Performing,

Moshe Kaplan