Performance; improving the speed of Simpletest during development

Setting up a test slave for performance

• Tweak MySQL configuration
  InnoDB, while recommanded for production systems, is not ideal on a test slave because DDL operations (CREATE TABLE / DROP TABLE) tend to be much slower then MyISAM's.
• Move MySQL database to tmpfs
  The test slave will stress the database server by issuing a lot of heavy queries (especially DDL queries) in a short period of time. After some of those queries, the database server explicitely flushes data to disk (MySQL tries to avoid that when possible, but it still calls fsync() after a DDL operation). Moving the database files to a tmpfs filesystem makes a lot of difference.

Tweak MySQL configuration

Add the following to your my.cnf:

Moving MySQL database to tmpfs

Tmpfs is a linux pseudo-filesystem that stores files and directory in memory. Files placed on a tmpfs will be lost after a reboot, but it doesn't matter for a test slave.

To move the test database to tmpfs, add the following line to your /etc/fstab:

<uid of the mysql user> and <gid of the mysql group> can be found in /etc/passwd and /etc/groups, respectively.