All data centre facilities are graded using a tier system. There are four tiers of data centre from 1 through to 4. The tier system is a standardized methodology used to define the uptime of a data centre. This is especially useful for measuring data centre performance, investment and return on investment.
Tier 4 data centres are considered as the most robust and less prone to failures. Tier 4 facilities are designed to host mission critical servers and computer systems, with fully redundant subsystems (cooling, power, network links storage etc.) and compartmentalised security zones controlled by advanced access controlled methods. Tier 1 facilities are the simplest that are generally utilised for non-mission critical emails.
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