Can be divided into tiers with a total of 4 levels as follows;
Tier 1 systems must be up and running at least 99.671% or within one year the system can be ‘crashed’ or ‘unusable’ for no more than 28.8 hours, but there is no redundancy.
Tier 2 systems must be up and running at least 99.741% or within one year the system can be ‘crashed’ or ‘unusable’ for no more than 22 hours, with redundancy required.
Tier 3 systems must be up and running at least 99.982% or within one year the system can be ‘down’ or ‘unusable’ for less than 1.6 hours, with redundant systems, redundant power and redundant Internet connections.
Tier 4 systems must be up and running at least 99.995% or within one year the system can be ‘down’ or ‘unusable’ for less than 24 minutes, with redundant systems, backup power, backup internet connection. And everything related to the system in IDC has to have a backup, such as air conditioning systems, fire suppression systems, etc.