I'm trying to understand UPS settings

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Level 2

279 points

I'm trying to understand UPS settings

I have just attached a UPS to my Mac mini Server (10.6.7 Server). I'm trying to understand UPS settings. In Energy Save, in the Power tab the computer is set to restart after power failure. In the UPS tab restart after power failure is switched off and the shutdown options are set (when 5min UPS power left and when UPS below 5%).

Now, what I want is that if power fails the computer runs on UPS until the batteries are drained. Then, when almost no power is left it should perform a normal shutdown. When power is restored, the computer should boot again. Have I set it like this now? Or should I set "restart after power failure" in the UPS tab as well? The Help does not give any info.

The UPS is an APC Smart-UPS 750 which is automatically recognized by 10.6.7 Server.

2010 iMac 27" i7, 2009 MBA SSD, 2010 mini server, NeXTdimension Cube

Posted on Apr 28, 2011 11:49 AM

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Answer 1

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Michael Black

Level 10

80,268 points

Apr 28, 2011 12:06 PM in response to Gerben Wierda

Yes, if you want it to reboot when power is restored, you need have the UPS come back on (i.e. UPS restart after power failure = ON). What should then happen is when the battery reaches the limits you've set, OS X should initiate a shutdown (any open apps/files may loose any changes since last save). Once the UPS detects no load from the computer, it should shut off (to conserve whatever battery power remains). Once the mains come back on, the UPS should wake back up, pause while it runs it's diagnostics, then it should reconnect power to the battery circuits and your computer should then reboot.

The only thing to remember is that the OS X shutdown script is pretty simple (basically a "shutdown -h NOW" command) which gracefully shuts down the OS (parks hard drives as well), but does nothing to gracefully shutdown 3rd party programs you may have running - they just get cut off as the system quits.

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Answer 2

Gerben Wierda Author

Level 2

279 points

Apr 28, 2011 1:08 PM in response to Michael Black

But what if the UPS also powers an external hard drive? There will still be load even if the computer has shut down. I guess it will run down until empty and then the same scenario plays out.

I guess I am going to do a full test anyway. But thanks for the answer.

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Answer 3

Apr 29, 2011 5:13 AM in response to Gerben Wierda

Ture, as long as something is connected to the battery plugs on the UPS it will just keep running until the battery dies. Unless, the external is also connected to the computer and powers on/off along with it. I use a MyBook 1TB external USB2 drive for my MBP's time-machine volume, and it will power off when the computer shuts down. If your drive behaves the same way, then you would be fine with your setup (and the drive should power back up when the computer re-boots on power resumption).

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