SafeSleep doesn't work for Mac mini

Question

I use Mac mini (Mid 2011)  with  hibernatemode=3.
But my Mac doesn't reboot from sleepimage afer I unplug the power cord. I mean SafeSleep doesn't work for my Mac. It boots normally but every program is initialized.
It is strange that I very rarely watch the very moment that my Mac's progress bar when rebooting from SafeSleep successfully.
Please help me to use SafeSleep and to save energy.
I am sure settings are correct and sleepimage is made by the following commands.
$ ls -l /private/var/vm
total 8519680
-rw------T  1 root  wheel  4294967296  9  9 18:01 sleepimage
-rw-------  1 root  wheel    67108864  9  9 18:02 swapfile0
$ pmset -g
Active Profiles:
AC Power        -1*
Currently in use:
hibernatemode        3
womp                 0
networkoversleep     0
sleep                10
powerbutton          1
ttyskeepawake        1
hibernatefile        /var/vm/sleepimage
autorestart          0
disksleep            10
displaysleep         10

Answer 1

Don't be too dismayed that you can't take advantage of Hibernate the way you did in the past on your PCs.  See this chart:
(from here: http://images.apple.com/environment/reports/docs/macmini_per_july2011.pdf)
At most, you're drawing 1.16W in Sleep.  For me, that amounts to a cost of about 10p every fortnight.  If it's the environmental effects that concern you, further reading of the PDF should show you've got one of the most environmentally-friendly home computers money can buy.
I hope that puts your mind at ease.