Scaling Drupal: Not IF..HOW

when scaling is a concern
	heavy page views
	logged in users

before live
	enable slow query log in mysql (my.cnf)
		mysqldumpslow - generates summary of slow query log file
		typicsl problmes
			poor/missing index
			data locking
			large result set
			slow, complicated query
		run identified queries using Explain
	load test
		simulate traffic
		populate db with test data
		how
			hp load runner
			openload
			jmeter - free from apache; java based; foxyproxy plugin for firefox; script use patterns on your site
	test with devel module

caching
	types of caching
		engines
			standard drupal cache
				part of core
				relies on database for storage
			apc 
				drupal cache + memory
				faster than memcached
				limited to single server; cache not shared across server
			memcache
				multi-server cache; network based
				a little slower than apc because it's network based
				limited control over when/how things disappear from cache
			static page cache/boost module
				drupal flexibility + performance of static files
				generally works only with anonymous users
	page cache
		full page
			generally only usefule for anon users
		block cache
			core in D6
			works with anon and registed users
			can set expiration and scope
			hard to explicitly expire cache
	programmatic cache
		static variable cache
			used by core
			within single request of single user
		programmatic data cache
			easily added to custom modules/themes
			explicitly using cache tables
			requires programmer knowledge of when to cache
			can become a problem of concurrency/timeliness

ongoing monitoring
	tools
		cacti
			free
			monitor various aspects like cpu, load, mem use, db activity
			trend visualization
			community add-ons
		mysql enterprise manager
		gomez

additional measures
	db scaling
		slave servers
			core does not really support horizontal scaling, but will in D7
		storage engine optimization
	hardware
		load balancers
	front-end techniques
		use Yslow! to get score on front-end speed; 
			free firebug extension
			shows potential optimizations
		js aggregation/compression
			aggregation supported as of D6 in core, module in D5
			aggregation just puts them all into one file, reducing requests
			minification not safe in PHP
				java shrinkers: dojo shrinksafe, minifier
		css aggregation
	apache tweaks
		set apache to gzip on server
		move .htaccess into http.config
	cdn
		content distribution network
		load static assets from several locations around world
		relatively cheap
		speeds up your server a little but user experience significantly
		offerers
			simplecdn
		some don't support https access