Hibernation (computing)

The rest, well Hibernation (English literally for " hibernation" ) and Suspend -to-Disk (English to German as: " swapping to disk " ) called, are two types of power-saving feature of modern computers ( such as PCs). In particular they are used in notebook computers, since there the saving of electricity during operation without power extends battery run-time.

Technical details

During hibernation, the computer is set by the user in a de-energized state, later to be able to continue working at the same place. In standby mode, however, only all parts of the computer are not required (such as the hard disk) as far as possible deactivated or turned off to reduce the current consumption as far as possible and at the same time to re-enable all the required parts as quickly as possible. Both this displacement in the resting state and reactivation usually requires considerably less time than a complete shutdown (but also much more time than in standby mode ). In addition, user input can be continued to the point just after interruption of work at, was stopped at the earlier. However, the restarting of the computer from hibernation does not constitute a restart, as he occasionally for software or system updates is required.

The technical implementation occurs in the conventional x86 PCs via the ACPI state "S4" ( " suspend to disk "). Switches the machine in this state, the contents of RAM is written to disk, and all system components are turned off. When you turn on the computer the image stored on the hard disk image is reloaded into memory (RAM). In addition, if necessary, the internal states of peripheral devices must be restored.

In contrast to the standby ( " standby " ) mode the computer in sleep mode turns off completely and tolerates a total separation from the power grid, for example when using a power strip with power switch incur no additional electricity costs.

Many operating systems such as Linux, Windows and Mac OS offer the possibility of activation of the resting state; usually the option is initially disabled.

Designations

Depending on your OS and language version, the names of Hibernate and Standby mode are different. So can mean something different than in Windows " hibernation " in Mac OS.

"Safe Sleep" includes both suspend-to - RAM and suspend-to -disk: The computer saves its state, both on disk and in main memory, the hard disk copy will only be used if during the quiescent state of a power loss, for example by an empty battery.

Windows

On Windows Vista and 7, there is at first glance only the mode " Power Save", which by default is designed as a hybrid mode. This means that it takes advantage of the standby mode and the sleep mode in a function. The mode, the system offsets in the standby mode (usually the state "S3 " - " suspend to RAM" ) and also writes the contents of memory to the hard disk or in stationary ReadyDrive and ReadyBoost flash memory. If you separate now from the mains and then switched it back on, the computer runs so high as if it were transferred to the idle state. PC Not unplugged the advantage of significantly faster reactivation of the computer out of standby mode is used. However, it is also possible to activate Vista and 7 the conventional idle mode.

Among the Microsoft operating systems, Windows ME, Windows 2000, Windows XP, Windows Vista and Microsoft Windows 7, the hiberfil.sys file is saved by default in the root directory of the system partition. Hyberfil.sys the file has the same size as the main memory. The idle state is supported on 32- bit operating systems only up to a memory size of up to 4 GiB.

Linux

A first implementation of " hibernation " functionality in Linux developed Gabor Kuti and Pavel Machek for the Linux kernel version 2.2, the end of the 90s. This resulted in the 2.4 kernel, so today partially used kernel module swsusp. Later, the modules suspend2 were pmdisk and uswsusp derived from swsusp. Although it is still practiced uswsusp of the kernel developers today use some Linux distributions in current spending even one of the other modules mentioned.

All responsible for hibernation functionality kernel modules work in the same way:

When you re- boot the system, the whole kernel is first loaded as usual. This checks before including the swap partition, if a hibernation image is stored on it. If it finds such, this is read and written back to memory. This is done instead of the initialization of the system services. (Daemons )

Mac OS

Macs built after mid-1999 switch at rest, the fans, the external devices and PCI cards from (so-called deep sleep, English for the "deep sleep ").

The mode "safe sleep" is only possible in newer Macs, x86 Macs dominate it all, in the last PowerPC Macs he may need in the Open Firmware instead of the normal "sleep " can be activated. The choice between "sleep " and "safe sleep" can not be controlled via the system settings, but depending on the device type (desktop or laptop) and built in by default.

However, it is possible to change this setting via a terminal command. The RAM contents are also stored in the "safe sleep" in a file. If during the rest state of the laptop battery to be empty, or turn the current work session can be restored automatically after a reboot. If the power is not interrupted, the computer wakes up just as fast as a simple "sleep ".