Availability

Tags

sys-design

Describes the expected uptime for a system over a certain period of time. For example the system must be available 364 days out of a year!.

We often measure availability as an annual percentage and commonly use the number of nines format. That is to say 5 nines means an availability of 99.999% out of a year. See more here.

For how availability varies in sequence and parallel systems, see here.