TABLE 1: The Nines of Availability
Uptime in Nines	Downtime (%)	Downtime per Year	Downtime per Week
One (98%)	2	7.3 days	3 hours, 22 minutes
Two (99%)	1	3.65 days	1 hour, 41 minutes
Three (99.9%)	0.1	8 hours, 45 minutes	10 minutes, 5 seconds
Four (99.99%)	0.01	52.5 minutes	1 minute
Five (99.999%)	0.001	5.25 minutes	6 seconds