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I recently did the Optibay mod on my 13" Macbook Pro, the stock magnetic drives now lives where the optical drive used to be. And an SSD has taken its place.

It's all good, but power consumption seems to have shot up as a consequence. I have tried various things but can't seem to get over this. I was contemplating unmounting the drive at boot time and manually mounting it when I need to use it (its a data/backup drive so only used occasionally) but I'm not sure this will work.

Does anyone have any knowledge of this?

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  • It will use more power when it is spinning. However, if it is set to spin down after a short amount of time of inactivity then I'm not sure you would gain much by unmounting it. But either way it should be fairly easy to test by leaving the machine idle on battery for a few minutes with the drive mounted/unmounted. I think there are apps to show time remaining like the built in behaviour in Snow Leopard. – James P Nov 1 '12 at 17:23
  • I'm sure you're right. However I can't find a command or app that allows these settings to be set on a per-drive setting - i.e SSD never sleeps, HD sleeps ASAP. – 5arx Nov 1 '12 at 20:14
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    This thread is very similar and may be of some help: superuser.com/questions/251969/…. I would ignore the accepted answer though. – James P Nov 2 '12 at 11:02
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An unmounted drive will not react to system sync(2) calls. Consequently it will remain idle (spun down) and not contribute much to power consumption. To alter how soon the drive spins down, you may use the pmset(1) utility as described to some extent in this answer

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    I was under the impression that pmset cannot be set per drive either. I think the OP was worried about the long-term effect it would have on an SSD - there doesn't seem to be definitive information available. – James P Nov 7 '12 at 10:52
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    @James I think pmset is a global rather than per-drive setting. And AFAIK from my googlings, the general consensus seems to be to leave SSDs alone and awake. – 5arx Nov 7 '12 at 14:25
  • Is there any drawback to sleeping an SSD? They are so fast that I can't imagine much of a performance hit. And if it shaves 2 months off the 10 year lifetime due to some esoteric caching internals, that's probably acceptable too. – Demis Nov 8 '15 at 5:21

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