Hi I have a VPS and one particular site is apparently causing the server to crash and I am getting alerts about lots of IO going on. How can I troubleshoot to see what is causing the extra load?
1) Try WordPress › WPDB Profiling « WordPress Plugins to see what is running all the queries.
2) Clearing post and page revisions will greatly reduce the size of a WP database - up to 90% in some cases - with a huge return in speed and lower server load. Run as SQL query in phpmyadmin to delete revisions; change table prefix as necessary:
DELETE a,b,c FROM wp_posts a LEFT JOIN wp_term_relationships b ON (a.ID = b.object_id) LEFT JOIN wp_postmeta c ON (a.ID = c.post_id) WHERE a.post_type = 'revision'
Then optimize all tables. And then add
define ('WP_POST_REVISIONS', FALSE);
near the top of wp-config.php to disable future revisions.
3) Check your permalink structure: Category in Permalinks Considered Harmful » Otto on WordPress
Try to deactivate all your plugins, activate the default wp theme, and check the load,
If the load is normal then one by one start activating the plugins,
This will help you to trigger which plugin or theme is affecting the load on server,
If this also doesn't solves then optimize your database tables through phpmyadmin, and also see whether your wp is updated or not.
This will be the best practice to troubleshoot the load.