Graceful shutdown and hard shutdown are two opposing methods of turning off a computer. A graceful shutdown is when a computer is turned off by software function and the operating system [OS] is allowed to perform its tasks of safely shutting down processes and closing connections. A hard shutdown is when the computer is forcibly shut down by interruption of power.
Graceful shutdowns are generally performed intentionally by users, as a part of their daily routines, at the end of a work day or when finished with home use of a computer. Hard shutdowns maybe unintentional due to power disconnects, electronic protection circuits or hardware failures. In the case of some safety issues like computer fires or security issues like malware or hacked computers, hard shutdowns may be as a safety precaution by users or IT departments.
Generally, a graceful shutdown is preferable in the case of any OS that saves its state. When the standard shutdown procedures are not done with these OSs, the result can be data corruption of program and operating system files. The result of the corruption can be instability, incorrect functioning or failure to boot.
Many modern OSs and other software are fault tolerant and generally handle the odd power interruption without issue. Both Bare metal and virtualized systems can be affected by hard shutdowns, so they should be avoided when unnecessary. Virtual machines [VM] may need to be restored from backups, while bare metal systems may even require a full reinstall.
This was last updated in October 2018
Continue Reading About graceful shutdown and hard shutdown
- Emergency power systems in data center disaster recovery planning
- Build a data center shutdown procedure to prepare for the worst
- How to Select an Uninterruptible Power Supply [UPS] for Your Computer
- Are you shutting down your computer correctly? Here's why it matters
- How UPS devices can protect a virtualization host
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 into doubt. Regular power cycling tests proactively monitor system performance and identify potential hardware failures arising from a hard restart. These tests can also 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.
Power cycling is often done remotely using systems management tools that stop/close applications, close any open data files, and then finally 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 cannot 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 are not closed first.
This was last updated in January 2017
Continue Reading About power cycling
- Use power cycling to avoid hardware failures
- Extend a server's lifespan with these maintenance tips
- Develop a strong power module with regular power cycling tests
- Power cycling is a calculated risk, but worth it
Dig Deeper on Data center hardware and strategy
-
data center resiliency
By: Paul Kirvan
-
Data center power terms to give your vocab a jolt
By: Jessica Lulka
-
How to shut down and restart a remote computer
By: Stephen Bigelow
-
Is your VM frozen? Isolate the cause and problem solve
By: Stephen Bigelow