A hard drive is a piece of hardware used to store digital content and data on computers. All computers requires secondary storage to store data on a long term and not lost in case of a power loss. Secondary storage devices are of two types: hard disk drives (HDD) and solid-state drives (SSD).
Hard disk drives are made up of magnetized disks—known as platters—that spin rapidly, typically somewhere between 5,400 and 15,000 RPM.
The faster the magnetic disk rotates, the quicker your computer is able to access information from it.
Hard drives generally come into two different form factors which are 2.5-inch and 3.5-inch. The form factor of hard disks denotes the diameter of the disk platter inside the hard disk.
2.5 inch vs 3.5 inch
1. The size will be 3 inch and 4 inch respectively.
2. 2.5 is used in laptops, desktops and servers while 3.5 inch in desktop and servers.
3. 2.5 inch draws less power compared to 3.5 inch due to the moving mechanical parts.
4. 3.5 inch will have a higher cache size.
5. 3.5 inch will have higher RPM
6. 3.5 inch will have a higher capacity.
7. 3.5 inch can transfer more data as the number of sectors per track in a disk platter is more. For same spin speed 3.5 inch will perform better.
8. Due to tighter and smaller construction as well as complex design 2.5 inch will be expensive.
9. 2.5 inch is added with accerelometers which can detect shock and park its head. This minimizes the impact.
10. 2.5 inch can be used in a 3.5 inch adaptor.
Source: 2.5 VS 3.5 HDD: What Are the Differences and Which One Is Better? – MiniTool