2109 Views 5 Replies Latest reply: Sep 24, 2008 2:06 PM by Kappy
I don't see why you would use a UPS on a laptop that has a battery connected and is running from n AC adaptor. The battery is the UPS.
I would presume that you could get the UPS to kick in only after the laptop battery has depleted or if you remove the battery. The latter would be ill-advised because it would trigger a reduction in processor speed.
The issue is not with the MacBook itself, but the external disks that are connected to it. The UPS will protect them for a given amount of time and then it too will lose power. So I need to be able to automatically shut the computer down so that there is no IO going to the disks when the UPS runs dry.
Obviously the internal battery will keep the MacBook going for considerably longer than the UPS, but the OS really doesn't like active volumes disappearing and it's running as a server and OS X Server like losing volumes that are shared even less. And if there's anything in the drive cache when the power goes out that's a recipe for corruption (which just happened recently)
If the battery provides adequate protection against a power outage, then you should be able to shut everything down gracefully without needing a UPS. If you need to be sure the drives are running then use external power bricks for them and connect them to the UPS.
If your UPS cannot protect the system better than the computer's battery, then I'm guessing you don't have a big enough UPS.
If just needing to shutdown gracefully after a power outage, then you should only need about 10 or 15 minutes of battery support at best. Or perhaps you haven't explained the situation adequately and I'm missing your intent.
I obviously didn't explain this as clearly as I thought.
1. MacBook Pro running OS X Server (i.e. on all of the time and I won't necessarily be in front of it during a power outage)
2. It has external disks hooked up which can be powered off safely as long as the server is not running.
I'm just looking for the graceful shutdown that is integrated in the Energy Saver Control Panel while connected to a UPS. The options are visible but not accessible (i.e. greyed out).
So the shutdown would only be for the computer? If it's running on battery and the battery is too low to keep it running, then the computer sleeps automatically. Would this not be the result you need?
This is from one of Apple's KB articles:
Tip: When the battery reaches "empty", the computer is forced into sleep mode. The battery actually keeps back a reserve beyond "empty", to maintain the computer in sleep for a period of time. Once the battery is truly exhausted, the computer is forced to shut down. At this point, with the safe sleep function introduced in the PowerBook G4 (15-inch Double-Layer SD) computers, the computer's memory contents have been saved to the hard drive. When power is restored, the computer returns itself to its pre-sleep state using the safe sleep image on the hard drive.