Today is the age of digitisation but at the same time to keep data is equally important. As you know to keep your important text, images, video, digital document in the form of data matter for you. Its very important when your hard disk of Desk Top of lap top get full with storage then it becomes essential to purchase external hard disk. The two most common form factors for modern HDDs are 3.5-inch, for desktop computers, and 2.5-inch, primarily for laptops. HDDs are connected to systems by standard interface cables such as PATA (Parallel ATA), SATA (Serial ATA), USBor SAS (Serial attached SCSI) cables.