By default, OS X computers put themselves to sleep automatically. This is good on client computers, but bad on servers, which should always be accessible. Therefore, an important step to setting up an OS X Server is to tell the server not to go to sleep, so that you will still be able to share files, manage iOS devices, and access that shopping list whenever you need it.
Manage energy settings by clicking on the System Preferences under the Apple menu and clicking on the Energy Saver System Preference pane. The slider for “Computer sleep” under Power Adapter should be set to Never with the “Display sleep” being set to a smaller number, like 20 or 30 minutes (many companies have security policies that govern this setting, so if you are setting Lion Server up at a company, verify that your choices meet your security requirements). Additionally, uncheck the “Put the hard disk(s) to sleep when possible” box and check the “Restart automatically if the computer freezes” box (Figure 2-4).
Figure 2-4. Configuring power management
If you are using an uninterruptable power supply (UPS) with your server and connect it to the server via USB, then you should also be able to use the Battery tab to configure how quickly the server shuts down when the battery goes off (check with the manual of the vendor who makes the UPS for more information on configuration).