I am owning Macbook Air, the problem i am facing is when i connect my external HDD to Macbook Air, (which is my backup drive also). the Net gets either disconnected or slows down.
MacBook Air (13-inch Mid 2013), OS X Yosemite (10.10.3)
USB 3 devices can interfere with Wi-Fi and Bluetooth. You may be able to mitigate the problem by using a USB cable with better shielding, or by switching from the 2.4 GHz wireless band to the 5 GHz band.
