Hi I want to know how many times of server downtime per year in 99.5% availability.
+3
A:
365 * 0.005, which is 1.825 days, which is 43 hours. That's how long your server can be down over a year.
It can be down for all 43 hours, or for 7 minutes each day in one year, or almost an hour in a week.
See this for more info.
Anton Gogolev
2010-03-03 12:25:13
To be picky, I'd use 365.25 to account for leap years.
mpez0
2010-03-03 12:29:32
don't forget leap seconds -> http://en.wikipedia.org/wiki/Leap_second
ThanosPapathanasiou
2010-03-03 12:45:12
@mpez0: to be picky, 99.5% availability just changes the downtime you're allowed during leap years.
Jimmy
2010-03-04 01:29:14
A:
60 * 24 * 365 (or 366 in a leap year) * 0.005 = 2628 minutes or roughly 44 hours.
ZombieSheep
2010-03-03 12:25:42
+1
A:
365.25 * 24 * (100-99.5) / 100 hours
Just replace 99.5 with whatever the percentage is.
Stephen
2010-03-03 12:26:43
+1
A:
Joel wrote a good article about server downtime you should check it out.
ThanosPapathanasiou
2010-03-03 12:29:22
A:
Depends on your assumptions for how long each outage takes to repair. Your total outage time, for 99.5% availability is 365.26*24*0.005 = 43.83 hours. If you anticipate a bit under 1 hour to repair the average outage and restore service, you may have 44 outages. If you have more complex problems that take a 4 hour average to solve, you may have 11 outages, or if all you need is a 10 minute reboot, you may have 263 outages and still achieve 99.5% reliability.
If you need to have parts express shipped overnight, you get one and a half outages per year.
99.5% is not a very high reliability figure for a production server.
mpez0
2010-03-03 12:37:19