Uptime
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Uptime is a measure of the time a computer system has been "up" and running. It came into use to describe the opposite of downtime, times when a system was not operational. The uptime and reliability of computer and communications facilities is sometimes measured in nines (similar to the unit of metallic purity). "Five nines" means 99.999% availability, which translates to a total downtime of approximately five minutes and fifteen seconds per year.
| Availability | per day | per month | per year |
|---|---|---|---|
| 99.999% | 00:00:00.4 | 00:00:26 | 00:05:15 |
| 99.99% | 00:00:08 | 00:04:22 | 00:52:35 |
| 99.9% | 00:01:26 | 00:43:49 | 08:45:56 |
| 99% | 00:14:23 | 07:18:17 | 87:39:29 |
It is often used as a measure of computer operating system reliability and stability, in that this time represents the time a computer can be left unattended without crashing, or needing to be rebooted for administrative or maintenance purposes. Long uptime can also indicate negligence as many critical updates require reboot on some operating systems.
The uptime(1) command on Unix systems will show the current time, the uptime, the number of users and load averages for the past 1, 5 and 15 minute intervals.
$ uptime 10:52PM up 1337 days, 7:45, 3 users, load averages: 0.21, 0.24, 0.23
The Uptime-Project, until 1 March 2007, collected data on uptimes from users, and the current record for longest uptime is 11 Years 303 Days 20 Hours 57 Minutes on a computer running OpenVMS. Rumours mention in January 2008 that Irish Rail had an OpenVMS machine up for 18 years[1], and restarted just for Y2K tests. The uptime of a personal computer is sometimes displayed as a badge of honour on an email signature or web site/forum. This was especially true in the Windows 9x days, where Windows NT and Windows 2000 users would boast of uptimes of more than 30 days, whereas many real-world Windows 9x installations crashed more often. In more recent times very long uptimes for home users with Windows NT and Windows 2000 machines are less striking because the Windows 9x line has been replaced by the Windows NT-based Windows XP.
Netcraft maintains the uptime records for many thousands of web hosting computers.
Users of Windows XP Professional, Windows Server 2003 and Windows Vista systems can type systeminfo at the Command Prompt to display all system information, including the System Up Time.
systeminfo | find "Up Time" System Up Time: 0 Days, 8 Hours, 7 Minutes, 19 Seconds
Users of OpenVMS systems can type show system at the command prompt:
$ show system OpenVMS V7.3-2 on node JERRY 29-JAN-2008 16:32:04.67 Uptime 894 22:28:52
Showing the uptime as days then hours:minutes:seconds
Users of UNIX systems (or equivalents) can use the uptime utility to get system information:
$ uptime 01:13:37 up 2287 days, 2:52, 25 users, load average: 1.76, 1.26, 0.70
[edit] See also
- Myth of the nines for a discussion of downtime and availability
- High availability
- Downtime
- Maintenance window
- List of Unix programs
- Reliability disambiguation page
[edit] References
[edit] External links
- Web sites with longest running systems by average uptime in the last 7 days
- The Uptimes-Project.org
- Tugs Uptime Project
- Uptime Project at The mrEriksson Network Broken since July 2007
- Free Website Uptime Monitoring Service
- Uptime Check
- Free website monitoring, reporting and alerting Service
- – Linux User's Manual
- Windows 9x 49.7 day bug
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