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I am wondering if it is bad or unhealthy to always put my Mac to sleep or should I shut it down instead? What I mean by putting it to sleep is that the display and hard drive are sleeping.

The reason for asking this question is I have heard from several computer literate people that sleeping the hard drive is not good for it.

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To play devil's advocate, what makes you think a designed mode of operation would be bad? Can you take this another level to explain what "bad/unhealthy" means? It's OK if you don't really know to leave this as is - but I wondered if you had a sharper more pointed question lurking below the initial inclination or wanted to know about a specific version of OS X or hardware. –  bmike Nov 1 '12 at 14:24
    
Never heard of something like this. Sound like a hoax. –  Max Ried Nov 1 '12 at 19:09
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4 Answers 4

up vote 8 down vote accepted

Anecdotally, the drives of 5 to 15 years ago would run longer if you never spun them down. When I managed servers - the drives failed less rapidly than the inexpensive hard drives that were in workstations (which typically spun down). It's not clear if we would have seen similar failure rates if we placed the higher priced (and presumably better built for the long run) drives in the workstations.

I have seen no credible studies that show any drive from the last 5 years lasting longer by disabling sleep. It's hard to imagine a case where you wouldn't want to have a computer sleep even if it were going to decrease the useful life of an inexpensive storage drive due to other components failing over time and the waste of energy.

We don't yet have good data on SSD wearing out either as OEM parts ordered from Apple or aftermarket SSD, but it will be interesting to see how they wear out due to write failures and if sleep writing of large RAM images will add up to enough writes to shorten the life of an SSD that otherwise would be healthy in the absence of storing sleep images.

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Anecdotally, the workstation drives I installed in inexpensive servers that never went to sleep in that timeframe also lasted longer—long past the point where their storage became laughably insufficient for any purpose. –  zigg Feb 19 at 3:02
    
And when I say anecdotally - I'm speaking of a population of between 1000 and 10,000 hard drives in one division. We clearly had enough drives failing to get a feeling of when and how they failed. However, we didn't have data like BackBlaze where they have 30k drives all made within 4 years of each other to collect data on failure rates. –  bmike Feb 20 at 0:13
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Laptops use a hybrid of sleep mode and hibernation by default: they both keep the RAM powered and write its contents to a sleep image.

The cells in SSDs can only be written to a limited number of times after which they become read-only. The write endurance of SSDs is often estimated as total bytes written (TBW), which is usually about 500-5000 times the capacity of the drives for high endurance SSDs.

If you had 8GB of RAM, half of it was written to a sleep image when going to sleep, and you put the computer to sleep 500 times per year for three years, it would be a total of about 6TB. For a 256GB SSD with a TBW of 200 times its capacity, that would be about 10% of the TBW.

That could be completely wrong though. I don't know any way to see how much data is written to the sleep image when going to sleep.

Related questions:

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I'd be curious to know whether safe sleep writes all 8GB or just the parts that are in use. If I get bored enough later, I might test this by comparing how long it takes for my power LED to start blinking when all 8GB is in use versus as little as possible. –  gabedwrds Nov 2 '12 at 13:51
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The main problem caused by putting macs to sleep is that the computer immediately writes all the data in RAM to the Hard drive. This means that if (as I've seen people do) you shut the lid of your Mac, then immediately start throwing it around, then there is a chance that your Hard drive could get damaged. However, so long as you are careful with it for a couple of minutes after putting it to sleep, then you should be fine. (In theory, the sudden motion sensor should park the drive heads before you do any damage, but I'm not sure how effective they are...)

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With great certainty we can say abrupt drops and shocks to a spinning drive that isn't yet sleeping is extremely hard on its mechanism. –  bmike Nov 3 '12 at 16:36
    
Abrupt drops in any circumstance will damage your laptop/computer. –  alexy13 Dec 31 '12 at 23:14
    
Of course, but the time just after the lid is closed is one of the worst times to do it... I was referring to general fast movement, rather than drops however. (Some people shut the lid, then immediately move the laptop somewhere, and often not gently...) –  daviewales Jan 2 '13 at 1:37
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First off, the "sleep" of a Mac differs from those of most other computers; Macs don't write the content of the entire RAM to the disk when you put it to sleep, it rather deactivates power supply to almost every component of the computer, except the RAM, so that, when the Mac awakes again, it never erased the RAM and kept it's content.

So it depends on what you call "bad/unhealthy", because the Mac is still powered, just not consuming as much. Meaning that Macbooks will lose battery life while sleeping, but it still may take up to weeks until it runs dry, depending on how much life the battery had when you put the Macbook to sleep.

My guess is that those "computer literate" people only knew about the sleep function of most other computers; those write the content of the RAM onto the disk when putting to sleep, and read it from the disk into the RAM when they awake. First: this may cause massive fragmentation for the disk. Second: SSDs lose life when writing on them, so this in particular may indeed be not healthy for them. Third: There is a risk of damaging the HDD while it is writing and you bump the laptop (however, this is not sleep related, and there should be technics put into the laptop to prevent this anyway).

Personally, I never really shut down my Macbook, except when I know I'm not going to use it any time soon. So again, I never shut down my Macbook, only just closing it.

EDIT: Just learned that portable Macs do both by default, that is keeping the RAM powered and saving the content to disk.

So yeah, the guys told you that technically are right, but as I see it, it's as unhealthy/bad for your drive as, well, using it for anything else.

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The contents of the RAM are also written to /var/vm/sleepimage by default on laptops. See pmset's man page. –  Lri Nov 2 '12 at 11:34
    
@LauriRanta ah yeah, right... "Safe Sleep". forgot about that one, but never knew it is the default setting. –  user33953 Nov 2 '12 at 13:31
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