or google drupal scale or drupal scalability and you will come up with several hits on the first page of results, which can be useful after you figure out what each one means by "scalability". (Language can be tricky.)
I recently watched a video from Drupalcon with PHP’s original creator Rasmus Lerdorf, where he tested Drupal against other PHP frameworks. It came out better than most (much room for improvement of course). I'm not an expert but I would estimate that to have any system that does similar to what Drupal does, and in such a customizable and modular fashion, it would be in the same ballpark so far as scaling. On Drupal's side as well are a variety of modules and software to assist with more advanced caching and performance improvements. I have a site I'm moving from a custom CMS to Drupal. The custom system is a lot faster than Drupal - but as I'm not an expert programmer I have absolutely no hope of ever expanding it from the functionality it has right now - it's fast, but stuck as it is forever. A custom system tailored for the precise needs of only one particular site will always be faster (if done correctly), but then you have to write a new CMS for every site you make. As soon as you start making your custom CMS into a framework so you don't have to start over from scratch each time, it becomes more and more like Drupal - easier to use, and slower due to the overhead of catering to features you "might need".
If you turn on Performance caching for anonymous users, that traffic takes very little server resources (and less still if you add a module which removes any database interaction for anonymous user requests). It gets more complex for high levels of logged in users, as it would with every system. Make sure to also get the YSlow Firebug add-on, since a lot of potential slowdown happens on the client side, not just the CMS, so you need to optimize that.
I recently assessed the scalability of Drupal's core forum, which is (by my tests) one of the least scalable areas of Drupal (without more advanced caching and performance help), since it contains a bad query that can make the forum slow for even 1 user if the number of forum topics and replies is high (in the tens/hundreds of thousands range): How to cache a large Drupal forum for high performance? (includes performance stats graphed out)
(since the performance bottleneck shown there is almost entirely the fault of one or two queries, it's likely that will be fixed by Drupal 7... either way I plan to put funds into fixing this area if needed).
Comments
You may want to check this
You may want to check this similar recent forum thread
http://drupal.org/node/301379
or google
drupal scaleordrupal scalabilityand you will come up with several hits on the first page of results, which can be useful after you figure out what each one means by "scalability". (Language can be tricky.)Yes it's possible to scale
I recently watched a video from Drupalcon with PHP’s original creator Rasmus Lerdorf, where he tested Drupal against other PHP frameworks. It came out better than most (much room for improvement of course). I'm not an expert but I would estimate that to have any system that does similar to what Drupal does, and in such a customizable and modular fashion, it would be in the same ballpark so far as scaling. On Drupal's side as well are a variety of modules and software to assist with more advanced caching and performance improvements. I have a site I'm moving from a custom CMS to Drupal. The custom system is a lot faster than Drupal - but as I'm not an expert programmer I have absolutely no hope of ever expanding it from the functionality it has right now - it's fast, but stuck as it is forever. A custom system tailored for the precise needs of only one particular site will always be faster (if done correctly), but then you have to write a new CMS for every site you make. As soon as you start making your custom CMS into a framework so you don't have to start over from scratch each time, it becomes more and more like Drupal - easier to use, and slower due to the overhead of catering to features you "might need".
If you turn on Performance caching for anonymous users, that traffic takes very little server resources (and less still if you add a module which removes any database interaction for anonymous user requests). It gets more complex for high levels of logged in users, as it would with every system. Make sure to also get the YSlow Firebug add-on, since a lot of potential slowdown happens on the client side, not just the CMS, so you need to optimize that.
I recently assessed the scalability of Drupal's core forum, which is (by my tests) one of the least scalable areas of Drupal (without more advanced caching and performance help), since it contains a bad query that can make the forum slow for even 1 user if the number of forum topics and replies is high (in the tens/hundreds of thousands range):
How to cache a large Drupal forum for high performance? (includes performance stats graphed out)
(since the performance bottleneck shown there is almost entirely the fault of one or two queries, it's likely that will be fixed by Drupal 7... either way I plan to put funds into fixing this area if needed).
-- David
absolutecross.com
[new guide/lesson in progress: Creating a CCK and Views powered Drupal site - feedback welcome]