uptime

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.

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. Conversely, long uptime can indicate negligence, because critical updates can sometimes require reboots.

Records and comparisons

The Uptime-Project, collected data on uptimes from users until 1 March 2007, and the current record for longest uptime is 11 years, 303 days, 20 hours and 57 minutes on a computer running OpenVMS. Rumours mention in January 2008 that Iarnród Éireann had an OpenVMS machine up for 18 years,^[1] which was restarted just for Y2K tests.

Netcraft maintains the uptime records for many thousands of web hosting computers.

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 which was considered to have to low uptime, sometimes attributed to the 49.7 days GetTickCount^[2] overflow issue originally preventing uptime above 49.7 days^[3] with workarounds such as requiring technicians to perform reboot every 30 day^[4], 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long uptimes for home users with Windows NT and Windows 2000 machines are less striking because the Windows 9x line has been replaced by the Windows NT-based Windows XP.

Determining system uptime

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. Windows Vista Business 64bit does not have an "Up Time" variable but rather "System Boot Time".

C:\> systeminfo | find "Up Time"
System Up Time:            0 Days, 8 Hours, 7 Minutes, 19 Seconds

Also, Microsoft provides the Uptime utility (http://technet.microsoft.com/en-us/library/cc751311.aspx):

C:\>Uptime
SYSTEMNAME has been up for: 16 day(s), 4 hour(s), 24 minute(s), 47 second(s)

Users of Unix-like systems can use the uptime(1) utility to get the uptime, together with the current time, the number of users and load averages for the past 1, 5 and 15 minute intervals:

$ uptime
04:20:00 up 1337 days,  2:52, 25 users,  load average: 1.76, 1.26, 0.70

Users of OpenVMS systems can type show system at the command prompt:

$ show system /noprocess
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

See also

Look up uptime in Wiktionary, the free dictionary.

• Downtime
• High availability
• Maintenance window
• List of Unix programs
• System profiler‎
• Website monitoring

References

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 Finished
• Windows 9x 49.7 day bug
• Printable Web Hosting Uptime/Downtime Chart
• Article Discussing Five 9's