[benchmarks] MongoDB kicks MySQL's ass no matter the circumstances

A recent post in HN claimed that MongoDB doesn't scale well, because the performance drops after the indexes are bigger than the available memory.<p>Scaling with MongoDB (or how Urban Airship abandoned it for PostgreSQL) - http://news.ycombinator.com/item?id=2684423<p>I decided to put this claim to the test, so I set up an Arch Linux virtual machine with 128M RAM and wrote a quick and dirty benchmark test. The test is a simulation of a simple blog with N user accounts and M posts per account. It creates all accounts first, then it creates the same number of posts for each account. The posts are not created in a consecutive order, and they are indexed by their "account_id" field. Once all accounts and posts are created, the script runs a query to find all post per account for all accounts.<p>So this script does two things: 1. Writes a lot of records. 2. Reads all records using an index.<p>You can download it from Github and use it to test in your own environment: https://github.com/naturalist/MongoDB-MySQL-compare<p>I used MongoDB v 1.8.2 and MySQL 5.5.13. My laptop is a Toshiba Satellite with Intel Core i5 @ 2.53GHz, and the virtual machine I set up was with 128M RAM, running Arch Linux.<p>Here are the results of my tests:<p><pre><code> MongoDB 5000 accounts 50 posts each using MongoDB's native _id Create: 317 secs | 185.94 CPU Read: 595 secs | 480.64 CPU --- MySQL 5000 accounts 50 posts each Create: 322 secs | 99.77 CPU Read: 740 secs | 487.50 CP --- MongoDB 5000 accounts 50 posts each using an auto incrementing int for _id Create: 252 secs | 112.31 CPU Read: 520 secs | 218.29 CPU </code></pre> So it looks like that MongoDB is significantly faster not only when writing but when reading too. The above test completely exhausted the VM's memory and kept using the swap partition.<p>Next, I decided to really push the limits of both and ran the MongoDB test with 10,000 accounts and 300 posts each. That's 3 million records. It created the records in 3643 secs using 1831.45 CPU, and read the records in ~8000 seconds using ~3000 CPU.<p>MySQL could not complete the above test. The MySQL server froze and I had to manually kill the process and restart the server.<p>Disclaimer: I do not work for 10gen, I don't even know them. I'm just a guy who's considering MongoDB for his next project.