Capacity and Performance Management
Capacity and performance management is a service management practice that you don't need to know for the ITIL 4 foundation level exam. But we are going to cover it so you have a good understanding, because it is one you're going to run across the real world.
So, the purpose of capacity and performance management practice is to ensure that services achieve the agreed-upon and expected performance, satisfies the current and future demand in a cost-effective way. When you talk about performance, this is a measure of what's achieved by delivering a system, a person, a team, a practice or a service to do some sort of function. This is associated with a number of service actions performed in a given timeframe, and the time to fill that service action at a given level of demand.
Here's a good example - the vouchers you can purchase from itil.diontraining.com. When you order a voucher, their service performance metric is that you have it in your hand within ten minutes. That's really quick, right? Generally, you're going to get it in less than 30 seconds, but sometimes it could take a little longer.
Now, when talking about capacity, on the other hand, and you look at your service capacity, this is the maximum throughput that a configuration item or service can deliver. So, if you consider the capacity of your hard drive, it's how much data you can store. If you consider the capacity of your network connection, it's how fast it is. Is it 100 megabits per second? Is it one gigabit per second? Whatever it happens to be, that would be your maximum throughput for that configuration item.
Now, as you go through and look at your capacity and performance management, this is where a lot of the metrics come into place. If you're working in a technical realm and you're measuring server capacity and server performance, there's going to be lots of different metrics you're going to get. You don't just measure the outputs; you also measure the outcomes. Which is important among these metrics and measurements? Why are we measuring them? What are we hoping to achieve? Oftentimes in capacity and performance management, people lose sight of the bigger picture and they focus so hard on the individual metrics of capacity and performance that it becomes useless.
In the real world, you are going to run into capacity and performance management a lot, especially if you're a system administrator or a network administrator. Because those are things that you're trying to meet; those particular standards inside capacity and performance to meet the metrics you're given.