Great quote about caching…

“When building a big web application you layer caches on caches. Ideally the top cache (browser local cache) can service the entire request such as it happens on google.com. if that fails the next best thing is blazingly fast memcached. Failing that we have to aquire and compute some data which is hopefully cached. If that fails the database gets the data from its cache or from disk. If that fails than the database files are probably cached by the operating system. And finally we move the physical read head of the disk to fetch the database off permanent storage.”