I'm often asked how far vertically should Portal be stacked on a single server, and should it be, given the single point of failure a single server provides.
First of all, vertical scaling implies vertical clustering, meaning you host multiple cluster members (instances) within a single WAS configuration profile (node).
Vertical scaling, or clustering, is a really, really good way to take advantage of available server resources. If you deploy hefty servers in production with multiple CPUs and tons of memory, then you are likely running out of heap space before you run out of CPU, which is not good and not the best use of your server's resources (see my previous blog post on finding the performance sweet spot).
Vertical clustering is really easy to set up, especially with WP 6.0. It amounts to just a few clicks of the mouse within the WAS console to create a new cluster instance based on the local node's configuration - no additional tweaking is necessary. You can take vertical scaling only so far, though, before you have to scale out horizontally, adding additional server nodes to your cluster. How far you take your cluster vertically depends again on how many instances it takes to strike the appropriate balance between memory utilization and CPU utilization (refer to previously mentioned blog post). In general, you don't want to run out of CPU (pegged at 100% utilization 100% of the time) while you have plenty of available heap storage left (which means you should probably run fewer vertical cluster members), nor do you want to run out of heap storage before you exhaust the CPU (you have too few vertical cluster members).
The likelihood that you will lose a hardware component is low. With the proper balance between horizontal and vertical scaling, you can get the most out of your hardware's horsepower while also guarding against hardware failures.[Read More]