Hard disk drives (HDDs) work by rotating their internal platters. Only during rotation can data be read or written. It's been decades since they acquired the ability to stay online, but not running in standby state. This reduces horsepower and can also reduce wear produced by heat generation and mechanical use.
macOS automatically sends a signal to internal (on older Macs) and external hard drives telling them to shut down after a period of time in which there has been no access to the data stored on them. The next time a hard drive is needed, there will be a slight delay while the drive is spinning at full speed. Some people have an intermittent but continuous need for hard drive usage, and they find that the constant short delays add up – and they rightly worry about the frequent ups and downs causing their own set of disk problems. wear.
Apple provides a user-friendly way to control this behavior in System Settings via the “Put hard drives to sleep when possible” setting:
- On a Mac laptop, go to System Settings > Battery and click Possibilities. You can choose between Always (default) and three alternatives: Battery Only, AC Adapter Only, or Never. Battery or AC adapter only, puts a player to sleep when possible only with that power source, which may still be desirable. Will never do what it says: macOS never attempts to spin a disk down.
- On a Mac desktop, go to System Settings > Energy. There you can enable or disable the setting, as desktop Macs require a power adapter.
A Mac laptop has four options for putting the hard drive to sleep.
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A desktop Mac lets you turn hard drive rotation on or off.
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Some hard drives and macOS installations may ignore this setting and continue to spin a hard drive after a short interval. If you find this unacceptable, you can open Applications > Utilities > Terminal and enter the following command followed by a return; enter an administrative password when prompted:
sudo pmset -a disksleep 0
THE 0 means “never”, but you can set a higher value in minutes, like 30 to mean “30 minutes”.
You can't issue a command line instruction to reset the hard drive sleep time to the default, which appears to be 10 minutes on an otherwise unchanged Mac desktop I tested on.
This Mac 911 article responds to a question submitted by igamesnews reader Howard.
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