How heavy for the server to transmit data over HTTPS?

I am trying to implement web service and web client applications using Ruby on Rails 3. For that I am considering to u开发者_StackOverflow中文版se a SSL but I would like to know: how "heavy" is it for servers to handle a lot of HTTPS connection instead of HTTP? what is the difference of response time and the performance at all?

The cost of SSL/TLS handshake (which takes most of the overall "slowdown" SSL/TLS adds) nowadays is much less than the cost of TCP connection establishment and other actions associated with session establishment (logging, user lookup etc). And if you worry about speed and want to save any ns of time, there exist hardware SSL accelerators that you can install to your server.

It is several times slower to go with HTTPS, however, most of the time that's not what is actually going to slow your app down. Especially if you're running on Rails, your performance scaling is going to be bottlenecked elsewhere in the system. If you are doing anything that requires the passing of secrets of any kind over the wire (including a shared session cookie), SSL is the only way to go and you probably won't notice the cost. If you happen to scale up to the point where you do start to see a performance hit from encryption, there are hardware acceleration appliances out there that help tremendously. However, rails is likely to fall over long before that point.