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#MacOSX : Disable Hibernation & SSD Tweaks

SSD are based on NAND Flash which have limited writes life. Currently 25nm chips support 3000-5000 cycles then they become read only.

This limitation makes very important avoid unneeded writes on the disk.

Moreover power save technologies can give some trouble (of course on SandForce controllers).

So this are some steps to Tweak your host system to give you the best experience:

  1. Turn off hibernation. To do this, open terminal app and type:
    sudo pmset -a hibernatemode 0

    Enter admin password and let’s do it the magic.
    This will prevent GB of writes every time you close the lid of your notebook.

  2. Remove unused hibernation file to free up as much space as your RAM:
    sudo rm /var/vm/sleepimage
  3. Open System Preferences and go to Energy Saver, than uncheck
    Put the hard disk(s) to sleep when possible
    both on Battery and Power Adapter tabs.
    This will prevent disk freezes and beachballs.
  4. If you have a SATA 2 interface and a Nvidia chipset on your Mac, check to have 3 Gbps Negotiated Link Speed.
    Go to Serial-ATA section in System Information app to take a look of your disk(s).
    This will ensure optimal performance of SSD.

NOTE: there are more Hacks, like enabling TRIM for non Apple supported SSDs but they give more troubles that other therefore I advice against to engage in similar enterprises.

NOTE 2: WARNING!!! Apple MacBook Air and MacBook Pro Update 2.0 seems to change the way “safesleep” is handled. If you currently have safesleep disabled in order to free up the drive space required by the sleep image, this will cause it to come back and even setting hibernatemode = 0 won’t change it. Quick untested FIX:

cd /var/vm
sudo rm sleepimage
sudo ln -s /dev/null sleepimage
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