so im looking for an external hard drive (250gb), and it never occurred to me, but there are hard drives that require a power adapter to power the HDD, then a usb to transfer files. The HDD i am use to are powered through a usb and transfer through the same one. i feel that its safer to go with a HDD with a power adapter, while the ones with just usb are only for portability. im going for one with a power adapter because my HDD is going to be stationary most of the time, but i still want to know if there is a real difference.
3.5" drives need power adapter as motor needs 12v which the usb can't provide as it is 5v. 2.5" drives use 5v but some need double ended cable into pc usb ports for extra power wereas others only need single usb port for power.
For 2.5" drives, I prefer the USB powered ones. The power adapters that most enclosures come with are so crummy that I prefer to use the USB power...it is almost always closer to the correct voltage than a cheap AC adapter. If you have a lot of USB devices, and don't have enough power for all of them, you can always use a powered hub, or even a generic USB charger.
