high availability table - just what those nines stand for ...

Availability %	Downtime per year	Downtime per month	Downtime per week	Downtime per day
90% ("one nine")	36.5 days	72 hours	16.8 hours	2.4 hours
99% ("two nines")	3.65 days	7.20 hours	1.68 hours	14.4 minutes
99.9% ("three nines")	8.76 hours	43.8 minutes	10.1 minutes	1.44 minutes
99.99% ("four nines")	52.56 minutes	4.38 minutes	1.01 minutes	8.66 seconds
99.999% ("five nines")	5.26 minutes	25.9 seconds	6.05 seconds	864.3 milliseconds
99.9999% ("six nines")	31.5 seconds	2.59 seconds	604.8 milliseconds	86.4 milliseconds
99.99999% ("seven nines")	3.15 seconds	262.97 milliseconds	60.48 milliseconds	8.64 milliseconds
99.999999% ("eight nines")	315.569 milliseconds	26.297 milliseconds	6.048 milliseconds	0.864 milliseconds
99.9999999% ("nine nines")	31.5569 milliseconds	2.6297 milliseconds	0.6048 milliseconds	0.0864 milliseconds