Check the man page
You can mess things up - stick with 0, 3, or 25.
SAFE SLEEP ARGUMENTS
hibernatemode takes a bitfield argument defining SafeSleep behavior. Passing 0 disables SafeSleep alto-gether, altogether,
gether, forcing the computer into a regular sleep.
____ ___1 (bit 0) enables hibernation; causes OS X to write memory state to hibernation image at sleep
time. On wake (without bit 1 set) OS X will resume from the hibernation image. Bit 0 set (without bit 1
set) causes OS X to write memory state and immediately hibernate at sleep time.
____ __1_ (bit 1), in conjunction with bit 0, causes OS X to maintain system state in memory and leave
system power on until battery level drops below a near empty threshold (This enables quicker wakeup
from memory while battery power is available). Upon nearly emptying the battery, OS X shuts off all
system power and hibernates; on wake the system will resume from hibernation image, not from memory.
____ 1___ (bit 3) encourages the dynamic pager to page out inactive pages prior to hibernation, for a
smaller memory footprint.
___1 ____ (bit 4) encourages the dynamic pager to page out more aggressively prior to hibernation, for
a smaller memory footprint.
We do not recommend modifying hibernation settings. Any changes you make are not supported. If you
choose to do so anyway, we recommend using one of these three settings. For your sake and mine, please
don't use anything other 0, 3, or 25.
hibernatemode = 0 (binary 0000) by default on supported desktops. The system will not back memory up to
persistent storage. The system must wake from the contents of memory; the system will lose context on
power loss. This is, historically, plain old sleep.
hibernatemode = 3 (binary 0011) by default on supported portables. The system will store a copy of mem-ory memory
ory to persistent storage (the disk), and will power memory during sleep. The system will wake from
memory, unless a power loss forces it to restore from disk image.
hibernatemode = 25 (binary 0001 1001) is only settable via pmset. The system will store a copy of mem-ory memory
ory to persistent storage (the disk), and will remove power to memory. The system will restore from
disk image. If you want "hibernation" - slower sleeps, slower wakes, and better battery life, you
should use this setting.
Please note that hibernatefile may only point to a file located on the root volume.