I can give you an example where speed and scalability are different.
Step 1: Create two WordPress blogs served by two Apache servers — one with KeepAlive on and one with it off
Step 2: Benchmark the speeds — you'll see that the KeepAlive one is faster
Step 3: Get a link to each blog on Daring Fireball
Step 4: Notice which server is still accessible (hint: not the faster one)
The server with KeepAlive will fulfill requests faster up to a certain number of people within a certain time span, but past that number it will simply start turning people away while the other server keeps delivering pages a little bit more slowly because Apache's KeepAlive trades capacity for speed.
At any rate, in a real production environment, there are measures you can take to make sure your site is both scalable and fast. Toy examples of poor configurations aren't very informative IMO.
Step 1: Create two WordPress blogs served by two Apache servers — one with KeepAlive on and one with it off
Step 2: Benchmark the speeds — you'll see that the KeepAlive one is faster
Step 3: Get a link to each blog on Daring Fireball
Step 4: Notice which server is still accessible (hint: not the faster one)
The server with KeepAlive will fulfill requests faster up to a certain number of people within a certain time span, but past that number it will simply start turning people away while the other server keeps delivering pages a little bit more slowly because Apache's KeepAlive trades capacity for speed.
At any rate, in a real production environment, there are measures you can take to make sure your site is both scalable and fast. Toy examples of poor configurations aren't very informative IMO.