I wanted to use a RAM disk for my MySQL data files when running my tests for a Rails project. I succeeded, but it only cut 2 seconds off of my ~30 second test suite for my functional tests, and didn’t cut any time off of my unit tests. But nevertheless, here is how I achieved this, in case it is useful to others. All of this is on OS X, using MySQL 5 from Macports.
What we are doing is creating a RAM disk, and then creating a seperate MySQL instance that stores its data on that RAM disk.
# Create the RAM disk
hdid -nomount ram://52428800
mount -t hfs /dev/disk1 /tmp/ramdisk1
# Initialize the MySQL environment
# Start the MySQL server
/opt/local/libexec/mysqld –basedir=/opt/local –datadir=/tmp/ramdisk1 –pid-file=/tmp/mysql_memory_localhost.pid –port=10000 –socket=/tmp/mysql_memory.sock
# Create your test database
mysqladmin5 –socket=/tmp/mysql_memory.sock -uroot create projectname_test
Now in your database.yml file, add
socket: /tmp/mysql_memory.sock to the test database configuration.
(thanks to this tutorial for how-to create a RAM disk in OS X)