Is Magento usually so terribly slow?
This is my first experience with it and the admin panel simply takes ages to load and save changes. It is a default installation with the test data.
The server where it is hosted serves other non-Magento sites super fast. What is it about the PHP code that Magento uses that makes it so slow, and what can be done to fix it?
If you haven't seen it yet, Magento and Rackspace teamed up to create a white paper on performance tuning Magento. It's excellent. https://support.rackspace.com/whitepapers/building-secure-scalable-and-highly-available-magento-stores-powered-by-rackspace-solutions/
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Another great resource, newly available (Oct 2011) is: http://www.sessiondigital.com/assets/Uploads/Mag-Perf-WP-final.pdf
(Thanks due to Alan Storm on this one.)
it will also come down to functionality versus performance.
Raw performance is gained using nginx, php-fpm, memcached, apc and a proper designed server.
Functionality like plesk and magento performance could be managed by taking the entire infrastructure in perspective when designing a magento performance cloud.
