Five 9s uptime - how much each 9 matters
"Since I saw Larry Borsato mention some figures in the 99.999% availability requirement-for-VoIP-networks debate, I decided it was time for me to dust off my networking theory book and implement Erlang's formula on an Excel spreadsheet using VBA, to get a better feel for how much each "9" matters.
Here are the results that I got:"
Availability Associated Downtime per Year 99% 87 hours and 36 minutes 99.5% 43 hours and 48 minutes 99.95% 4 hours and 23 minutes 99.99% 53 minutes 99.999% 5 minutes