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pros/cons of "put the hard disk(s) to sleep when possible" ?

A

Aven SkyGazer

macrumors regular
Original poster
Nov 12, 2008
112
0
13'' alum-uni mb

system preferences --> energy saver


what's the advantage/disadvantage of this seemingly nifty option?
 
When the hard disk is inactive for long times, the feature surely saves energy. When, on the other hand, it's inactive for short periods, the drive spins down and back up all the time, which may, in the end, theoretically use up more energy than just letting it spin constantly. Also, spinning down and back up might shorten the life of a hard drive, but I'm not certain about that.

Having stated all that, I myself most certainly have the feature turned on. My hard drive usually spins all the time when I'm using my laptop. It's only when I leave it unattended or when I let it sleep that the drive spins down. So constantly spinning down and back up is definitely not the case with my MacBook, as I think it is with most computers. That's pretty obvious, really, as Mac OS X constantly uses a portion of the hard drive for memory swap space.
 
In addition to what's already been saved, that option is really useless if you have a SSD.
 
Bengt77 said:
When the hard disk is inactive for long times, the feature surely saves energy. When, on the other hand, it's inactive for short periods, the drive spins down and back up all the time, which may, in the end, theoretically use up more energy than just letting it spin constantly. Also, spinning down and back up might shorten the life of a hard drive, but I'm not certain about that.
Click to expand...
That's why, for the most part, the OS is smart enough to know when it can sleep the drives. So it doesn't have to constantly start and stop them.
 
The default "wait to sleep" time on the hard disks is 10 minutes (according to 'pmset -g' on Snow Leopard with disk sleep on). If they're inactive for 10 full minutes, then it puts them to sleep. This, in all honest, does not occur much in active use, but is nice if you're leaving a computer on extensively.

The benefit is, as stated, some possible power savings. The downside is the slight slowdown to access the disk when it's been spun down, as well as the slight increase in wear on the disk. Due to the high timeout on the spindown, neither of these are a serious problem - and I'd definitely recommend turning/keeping disk sleep on.
 
Aven SkyGazer said:
what is an SSD and why doesn't it matter?
Click to expand...

a SSD is a "Solid State Drive" - it uses memory very similar to what you find in USB sticks and memory cards.

The advantage is that it doesn't use any moving parts which makes them a lot more resistant to mechanical damage. in HDDs you have spinning disks (similar to small DVDs) and a head which scans across the disk to read/write data from/to the disks, which makes them quite susceptible to mechanical damage.

The "put the hard disk to sleep" option doesn't affect SSDs, because they don't have any spinning parts which can be stopped to save energy. (They do, of course, save energy in the first place BECAUSE they don't have any spinning parts. :))

Fabian
 
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