power cycling
What is power cycling?
Power cycling is the process of turning hardware off and then turning it on again. In the data center, technicians use power cycling to test the durability and reliability of network components. It is commonplace for servers to operate for months or even years without a reboot or disruption. These long periods of uninterrupted operation can place the entire system's resilience and reliability in jeopardy.
Anyone can power cycle an electronic device; no training is needed. There might be situations, however, where prior knowledge of the impact of a power cycle is useful. Highly complex systems might have a specific power cycling process, perhaps using one or more steps to completely disconnect from the power source before reversing the process for a restart.
How does power cycling work?
When an electronic device, such as a laptop, modem, router or printer, isn't working properly, an initial troubleshooting technique is to complete a power cycle. The following steps are involved:
- Shut down the device.
- Disconnect it from its power supply.
- Wait 30 seconds.
- Plug the device back into its power source.
- Push the power button and power on the device.
This can clear issues in the central processing unit, firmware, operating system and associated apps, and typically the device or app should power up as normal.
Regular power cycling tests proactively monitor system performance and identify potential hardware failures arising from a hard restart. These tests can reveal the amount of downtime that can occur after an unexpected hardware shutdown, and ensure proper system reconfiguration and accessibility after a restart. It's a best practice to make sure these tests comply with other disaster recovery and shutdown procedures.
Remote power cycling
Power cycling is often done remotely using systems management tools that stop or close applications, close any open data files and then shut down power. This orderly shutdown process reduces the chances of accidental data or file corruption.
Once the power is off, the system is restarted remotely, using technologies such as Wake-on-LAN. Technicians often wait several seconds before restarting the system to ensure that any dynamic volatile memory has cleared completely.
If a system has become unresponsive or can't be shut down remotely, technicians can manually cycle power by holding down the physical power switch for several seconds, waiting several more seconds for memory contents to clear and then using the power switch to restart the system. This method, however, does risk some data loss if open applications or data files aren't closed first.
Restarting vs. power cycling
Power cycling is different from restarting a device and is used in different circumstances.
- Restarting. When conducting a device restart, the device is still running but the operating system (OS), firmware and apps restart. When there's a problem, a restart is a faster way to get a system working normally as opposed to a power cycle. Doing a restart can be helpful when the issue is thought to be software related. For example, if email isn't working properly, a restart can reboot the email app and clear the problem.
- Power cycling. Power cycling is similar to and often referred to as a hard restart. With power cycling, the power is completely disconnected from the device and then powered up again. Issues in memory and within the device are flushed out of both hardware and software. In situations where it appears the problem is with the hardware, a full power cycle is the recommended remedy.
Computer refresh vs. reset
A refresh of a computer or other device is used to improve its performance without affecting user files and settings. A reset, on the other hand, erases data and applications from the device, restoring it to its original state. The steps involved in both these processes vary depending on the OS. It's recommended that files be backed up before performing these operations.
Device or application refresh
A computer refresh restores a computer to its original state but doesn't affect personal files, documents and user settings. A refresh is used to clean up a device, remove applications that are no longer needed and improve performance. It reconfigures system settings without changing or deleting data, files or installed applications.
Applications can also be refreshed, returning them to their normal operating state. For example, if Microsoft Outlook on Windows is stuck in a loop or displays another minor issue, a refresh might fix the problem. There's no impact on power to the app; however, a power cycle or hard restart might be needed if the issue isn't resolved with a refresh.
Hard and soft reset
On a computer and other hardware device, a system or factory reset refers to a comprehensive process that erases everything on the device -- data, files, applications and user settings -- and restores it to the original out-of-the-box condition. This approach, also called a hard reset, provides a way to start fresh when dealing with significant software issues, malware or reconfiguring a machine to go to a new user.
A soft reset is analogous to restarting a device. It closes applications and clears data in random access memory. Unsaved data can be lost, but data stored on the hard drive, applications and settings remain unaffected. Some devices have reset buttons that can be used to quickly clear glitches affecting their performance. The power remains on during a soft reset. Soft resets are also referred to as soft power cycles and soft reboots.
Advantages and disadvantages of power cycling
Power management options are often an effective way to fix issues that are annoying or causing delays. Starting with a simple restart can be a good idea; a full power cycle is a more aggressive way to return devices to normal operation. If a major issue within the device or app is causing problems, more detailed actions must be taken.
Power cycling is an effective troubleshooting action. It provides an effective first step in addressing a system or application disruption. It costs nothing, takes very little time and is frequently the needed fix. There are risks to data and files especially. For more sophisticated systems that have a formal shutdown process, an arbitrary power cycle without proper preparation might result in unanticipated problems.
Power cycling can fix a lot of issues. Find out how one user used power cycling to solve wireless weirdness.
