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Set minutes until hard drive spins down System
As already noted in the comments in the comments on this hint, the time until the hard drive spins down can be controlled by editing the file /Library -> Preferences -> SystemConfiguration ->

Under the key "Disk Sleep Timer," you can edit the number of minutes until an idle drive goes to sleep. There are separate settings for AC Power and Battery. Sadly, the setting cannot be set per drive, but at least it prevents my external RAID from powering down after five minutes of inactivity.

[robg adds: This other hint explains how to do this using a program included with the Developer Tools. And, of course, if you don't want them to sleep at all, then just uncheck the 'Put hard disks to sleep when possible' box in the Energy Saver System Preferences panel.]
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Or, for a far easier solution...
Authored by: giskard22 on Oct 02, '06 09:11:47AM

Use the 'pmset' command, which allows you to edit all the Energy Saver stuff.

For disks to never sleep, you set the disksleep timer to 0.

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Set minutes until hard drive spins down
Authored by: Ockham on Oct 02, '06 01:38:48PM

Can anyone confirm whether this setting, or the other Developer tools hint noted, persists across different computers? I.E.- if I change this setting on a portable drive attached to my Desktop and then use this same drive on my laptop, or any other computer, will the spin down time reset to the default for the computer it is attached to?

I know that there are some utilities on the PC and Linux side that allow you to "hard code" the spin down setting to the drive and I am hoping this does the same.

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Set minutes until hard drive spins down
Authored by: tbolioli on Oct 02, '06 02:49:20PM

No, it most certainly does not. It is a system wide parameter.

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Bad solution / other hints address this properly
Authored by: rorya on Oct 03, '06 12:52:47AM

At the risk of sounding pedantic; this has been covered at least once before, with a hint I submitted years ago, which uses the "correct" solution. pmset(1) is the recommended tool to use. You should be using it, if you want to have fine grained control over the timeout of the various energy saver settings. This tool actually manages the plist mentioned in this hint. I really think it's always a good idea to refrain from editing the plists by hand, as it's a much more error prone process. On top of that as of 10.4 we're starting to see much more common use of the binary1 style plist for increased performance; and these don't work with a text editor.

For all of us hint contributors, we should always encourage the use of a supported tool to manage these plist files. There are many, many hints on this site that erroneously direct one to do these direct edits, rather than using the supported tools, like defaults(1). Probably as a result of experience on other unices, but this is a more rigid, layered system, so sticking to the management tools makes life much easier.

"Any sufficiently advanced technology is indistinguishable from magic" - Arthur C. Clarke

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Bad solution / other hints address this properly
Authored by: magir on Oct 05, '06 02:49:20AM

The main reason I submitted the hint was to make sure that searching for relevant keywords reveal the correct hint. Just a few seconds after submitting the hint I sent another mail to Rob asking him to add information about pmset but sadly he ignored that. So basically I agree with what you write - sometimes it simply should be possible to change hints after submitting them ;-).

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Yikes! Ext. HD Goes to Sleep At Will!
Authored by: davidas on Nov 10, '06 05:02:27AM

Hi, this seemed like an appropriate thread to post my question. I've got a LaCie FW 360 Extreme which goes to sleep, spins down after a few moments when not accessed. I've got the "Put the hard disk to sleep when possible" setting unchecked, but it doesn't affect this particular drive. In addition, I've got a 500 GB striped RAID zero and two other FW externals running with no problem. I've run diagnostics and repaired directories using DiskWarrior and DiskUtility to no avail. I've been using the drive as a scratch volume for media so these spin downs and ups are a real pain. Anybody have any ideas? I haven't installed Development Tools, but will I need to? Or should I just contact LaCie? Many thanks in advance for any help!

All the best,


David Smith

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Alternate Solution for WD Green Drive Auto-sleep
Authored by: Makosuke on May 05, '10 03:22:49PM

I'd at one point run across this hint when trying to figure out why my WD Green drives, connected to my Mac via a FW800 enclosure, would partly spin down CONSTANTLY, regardless of whether the Energy Saver pref was checked or not.

Turns out that among the power saving features of the GP series is auto head park, a feature that essentially puts the drives into a partial sleep state; the drives spin at least partway down (maybe all the way) and park the head after a period of inactivity. Problem: The default setting on the drives (both an older EADS model I was using and the new 64MB cache Advanced Format EARS models) is to do this after 8 seconds. Yes, 8 seconds. Meaning that they'll sort-of-sleep after almost ANY period of non-constant use, which is infuriating when you're trying to work on them.

Fortunately, WD has a utility that allows you to change the timing on (or disable completely) this feature. XLR8YourMac has a tutorial:

...which worked well enough for me. After disabling the head park (I figure if I want it to sleep I can just use the OS setting and change it with this hint or pmset) it appears to behave in a more normal manner.

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