If there is a single point of failure, can we simply add another identical server to solve it? The answer to this question is not as simple as a yes or a no. Even if we install the same software on two identical machines, how can we synchronize the data between them? It is not ideal to copy new data to the backup server manually. That's why the HA environment was created.
What does availability mean? Let's take a look at the formula to calculate the availability; we need to divide the subtraction of Downtime duration (DD) from Expected uptime (EU) with Expected uptime (EU) and then multiply it by 100. Availability is expressed as a percentage of uptime in a year. The formula is as follows: