From Longman Business Dictionaryfive ninesˌfive ˈnines (also five nines reliability) noun [uncountable]COMPUTING a computer or computer system with five nines reliability, or which has five nines, is almost certain never to break or go wrongOur server has just five minutes of downtime a year. That’s 99.999 per cent availability, the five nines to which other hardware companies can only aspire.
