How many nines uptime?
Uptime is an important concept in the operation of computer systems and their
applications. As we have become more dependent on computers, we have
also come to expect that they are always there to help us do our work.
We often hear terms like available 24/7/365 to mean that a system is supposed
to be up 24 hours a day, 7 days a week, 365 days a year, i.e., all the time!
It is recognized that systems require some downtime, periods of time that
they are unavailable, for regular preventive maintenance. Uptime is
usually used to characterize the unexpected outages. A system with
100% uptime would have had no downtime or unplanned outages during the
selected period of time.
But the reality is that computer systems fail, maybe due to a crashed hard
drive or a memory failure. There are also times that an application
such as email or calendaring may not be working.
The tables below show the maximum amount of time a system or
application can be down and still have the given amount of uptime.
Times are not listed if less than 1 second.
Our time definitions
1 day = 86,400 seconds
1 week = 604,800 seconds
| |
1 month = 2,592,000 seconds (30 days)
1 quarter = 7,862,400 seconds (91 days)
1 year = 31,536,000 seconds (365 days)
|
Two Nines Uptime - 99%
| Period | Maximum allowed downtime |
| 1 day | 14 minutes 24 seconds |
| 1 week | 1 hour 40 minutes |
| 1 month | 7 hours 12 minutes |
| 1 quarter | 21 hours 50 minutes |
| 1 year | 3 days 15 hours |
|
Three Nines Uptime - 99.9%
| Period | Maximum allowed downtime |
| 1 day | 1 minute 26 seconds |
| 1 week | 10 minutes 4 seconds |
| 1 month | 43 minutes 12 seconds |
| 1 quarter | 2 hours 11 minutes |
| 1 year | 8 hours 45 minutes |
|
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| | |
Four Nines Uptime - 99.99%
| Period | Maximum allowed downtime |
| 1 day | 8 seconds |
| 1 week | 1 minute 0 seconds |
| 1 month | 4 minutes 19 seconds |
| 1 quarter | 13 minutes 6 seconds |
| 1 year | 52 minutes 33 seconds |
|
Five Nines Uptime - 99.999%
| Period | Maximum allowed downtime |
| 1 week | 6 seconds |
| 1 month | 25 seconds |
| 1 quarter | 1 minute 18 seconds |
| 1 year | 5 minutes 15 seconds |
|
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| | |
Six Nines Uptime - 99.9999%
| Period | Maximum allowed downtime |
| 1 month | 2 seconds |
| 1 quarter | 7 seconds |
| 1 year | 31 seconds |
|
Seven Nines Uptime - 99.99999%
| Period | Maximum allowed downtime |
| 1 year | 3 seconds |
|
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