fjr wrote:What are recommended powersupply requirements for pi 2?
If the pi 2 is a server with no usb hard drive?
If the pi 2 is a server with a 2tb usb hard drive?
If the pi 2 used with peripherals, pc mouse, keyboard, etc and no usb hard drive?
If the pi 2 is used with peripherals, pc mouse ... and a 2tb usb hard drive?
Not possible for us to answer directly because you did not give the specifications of each device.
Here is how to figure this out for yourself:
The maximum current into the RPi is limited to 2A.
The maximum current to all of the USB ports combined is 1.2A so that leaves 0.8A for the RPi + anything connected to the GPIO's
You need to find the current draw specification of each USB device and add them up. If <= 1.2A then you should be OK as long as your power supply can deliver the power needed and still maintain the 5V +-5% voltage. If > 1.2A then you will have to use a powered HUB.
Note the default USB power output is 600mA. You must change a configuration setting to get the max 1.2A
So as mentioned you can't go wrong with a 2A supply. A smaller supply can be used for the server with no peripherals.
A larger than 2A supply can be used but has no added benefit.
Unless specified otherwise my response is based on the latest and fully updated Raspbian Stretch w/ Desktop OS.