Search code examples
requirementsuptimeservice-level-agreement

Is"always" a workable term to describe the uptime of a server?

since me and my colleagues had a discussion about this, I wanted to ask, if you would use the term "always" to describe the uptime of a server in a requirement.

Example: The server should be always reachable.

Since, in my opinion, alsways can't be measured, I would rather write the requirement like this:

The uptime of the Server should be >= 99%.

Thanks in advance!

Solution

  • Do not use always, it isn't possible to achieve. Uptime is discussed in terms of nines: https://en.wikipedia.org/wiki/High_availability#%22Nines%22

    Amazon S3 for example, offers 4 nines of availability (99.99%).

    Look at: https://uptime.is/ to fully understand how much downtime you are allowed for a given sla.