How the specific uptime requirement in Data Center Tiers i.e. Tier1 = 99.671 % , Tier2 = 99.741 % , Tier3 = 99.982 % & Tier4 = 99.995 % were decided ?
How can I build a 99.9999 % uptime system ? I have 40 servers , data base , deployment machine ; mirrored to a second data center . How do I handle patches ?