If you’re anything like me then you look at an uptime figure of 99% and automatically assume “that’s good” – but have you ever sat down and worked out exactly what that equates to in time?
I know I haven’t, but Pingdom have come to my/our rescue with their handy Uptime / Downtime Conversion cheat sheet.
One can see at a glance the difference between 99% and 99.9% uptime per month and per year. If you’re running a service that needs to remain up 24*7 then per month then it’s a difference of 6hrs 29m which increases to 3d 6hr 50m per year – suddenly 99% doesn’t look that good.
I wish Microsoft Exchange at our church had a 99% uptime. What is more scary is the the note that service providers don't count planned maintenance into up time numbers.
From long experience I know that planned maintenance is a necessary evil. So long as one is informed in enough time then this should never be a major problem. The trouble with a 24*7 society is that equipment fails – so we can either plan the fixes or we can react to them. Personally I prefer to plan.