No Sleep is a free portable program for Microsoft Windows computer systems that prevents external hard drives from entering sleep mode.
Some external hard drives make use of a hard coded sleep mode that kicks in after some time of inactivity; usually between 10-15 minutes. The external hard drive enters sleep mode then and initiates a wake up when data needs to be read or written.
This can be problematic in some circumstances, as it takes some time to exit sleep mode and become available. If that happens often, you may want to prevent the drive from going into sleep mode at all.
The developer of No Sleep has created a simple program that writes a blank text file every x minutes to the external hard drive effectively preventing it from entering sleep mode. The same can be done with a simple batch file, or Autohotkey program but No Sleep is a solution for users without the knowledge to create a program of their own.
The software program is portable and comes with a graphical user interface that can be used to configure some of the program's settings. The gui can be used to select an external hard drive that you want to prevent from going into sleep mode. Here you can furthermore define the write interval of the text file to the drive. The default is set to once per minute, but you may want to decrease the period a bit depending on the hard drive in question.
The interval can be set between 1 and 15 minutes. NoSleep mode can then be started with the click of a button. It is furthermore possible to place the software program in the Windows system tray to make it as unobtrusive as possible.
No Sleep should work on all versions of the Microsoft Windows operating system and with all kinds of hard drives that are connected to the computer system.
Update: No Sleep has been moved to a new location on the Codeplex website. The software has been last updated in 2009 which may indicate that the developer has stopped working on it. The latest version of No Sleep HD is still compatible with all current versions of the Microsoft Windows operating system.
Update 2: The developer has released NoSleepHD 2.0 which can be downloaded from the official program homepage. It ships with a new user interface and improved feature set.
Major changes include options to select more than one drive that you want to keep from entering sleep mode and an overview of all hard drives connected to your system and their type.
An alternative to NoSleep HD is KeepAliveHD which adds a couple of interesting features that NoSleep does not support. You can for instance use seconds, minutes and hours as the write interval, disable writing if the user of the system is not active, and set write intervals individually for each drive that you add to the application.
If you notice that one or multiple of your external hard drives (or internal for that matter) enter sleep state regularly, and that it takes too long before they wake up when accessed, then you may find No Sleep useful to prevent that from happening.
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