Honestly my impression was the “nines” of reliability just means how many nines your reliability starts with, as a decimal. I never thought much about it though.
I will also say it’s amusing that the debate is between one and two nines. Neither is objectively great. If you built a system with >3.65 days of downtime in a year that wouldn’t be something you’d brag about in an interview.
This is pretty pedantic, but I think it's usually rounded. 1=90%, 2=99%, 3=99.9%. I'd say 98% is "not even two nines" but not "one nine".
Honestly my impression was the “nines” of reliability just means how many nines your reliability starts with, as a decimal. I never thought much about it though.
I will also say it’s amusing that the debate is between one and two nines. Neither is objectively great. If you built a system with >3.65 days of downtime in a year that wouldn’t be something you’d brag about in an interview.