Most hard drives fall into these two sizes, and most have similar height and length within the same width category. Such systems are rarer among 3.5' drives, since desktop computers are usually designed not to be moved while working.Īs other answerers have indicated, 2.5' and 3.5' refer to the width of the drive platters. For example some 2.5' drives have accelerometers which can detect when drive is dropped and safely part drive head in order to minimize vibration damage. Usually high performance 2.5' drive will cost as much as high performance 3.5' drive but will have performance of mid-range 3.5' drive.Īlso 2.5' drives may be more resistant to vibration than 3.5' drives.

While these numbers change with each generation of hard drives, one thing that more or less stays constant is the difference between performance of the drives and the price difference. Their power consumption is lower and for example WD10TPVT by Western Digital uses up to 2.5 W.

The number of revolutions in minute is usually 5400, but may be as much as 7200. On the other hand large 2.5' drives are in the 1 TB range and usually have between 8 MiB and 16 MiB of cache. It is quite fine for desktop computers, but too much for battery operated devices. The downside is their power consumption which is generally around 5W. For example at this time, largest consumer 3.5' drives can store up to 3 TB of data, may have as much as 64 MiB cache memory and are 7200 RPM or 10000 RPM. Usually 2.5' drives have lower capacity, lower cache and lower angular velocity compared to 3.5' drives of similar price.

Another difference which is worth mentioning is that since 2.5' drives are mostly used in mobile computers, main goal during design was low power consumption and other important factors were considered a lower priority.

3.5 inches actual size