Not All 2.5” Drives Are Created Equal
While all 3.5” hard drives will fit into every 3.5” drive bay or hot swap frame as long as you use the correct interface, there are more differences in the 2.5” space. The UltraATA interface has finally been replaced by Serial ATA in the mainstream, which is why upgrade users have to pay attention: none of the 500GB hard drives are available with a parallel UltraATA interface. You will have to look for 250GB hard drive if you want to replace an existing notebook disk, as the latest models aren’t available with the older interface.
Spindle Speed Matters
In addition, rotation speeds and cache capacities may vary. While cache capacity does not have a significant impact on hard drive performance, spindle speed is extremely important. Faster rotation speeds lead to better throughput and to quicker access time, as there will be less rotational latency, which translates to waiting time.
Notebook hard drives are available in three different speeds: 4,200, 5,400 and 7,200 RPM. Obviously, the last of these is the quickest choice, but they consume slightly more power and potentially reduce battery runtime on your notebook a bit. However, there are always exceptions to this general rule, as you can see in the power consumption results of our benchmark section.
Enthusiasts want Flash SSDs
Drives running at 4,200 RPM will eventually die out, as there aren’t substantial cost savings or much better capacities compared to models at 5,400 RPM. The 7,200 RPM speed will remain the best for the time being; 10,000 RPM is a viable option for high-performance notebooks, although some sort of hard drive cooling might then be required. For these applications, solid state hard drives based on flash memory are the much better, but also more expensive, choice.
Finally, there are differences between 12.5 mm (Hitachi Travelstar 5K500) and 9.5 mm (Samsung Spinpoint M6) 2.5” hard drives. All of the flash based 2.5” drives fit into the 9.5 mm envelope, as the PCB with the flash memory chips and the controller can often even be fit into an 1.8” form factor. 12.5 mm drives, however, are usually more suitable for external storage or portable storage applications, where space restrictions usually do not apply.
Here is the difference between the 12.5 mm and 9.5 mm heights. Hitachi’s Travelstar 5K500 requires 12.5 mm of clearance.