Laptop hard drives are smaller variants of the larger desktop counterparts and generally emphasize power efficiency a lot more than raw capacity of groundbreaking performance. You will find fair a number of major industry stalwarts competing in the cutthroat laptop hard drive business: Fujitsu, Hitachi, Samsung, Seagate, and Western Digital.
Past generations of laptop hard drives trusted parallel ATA interfaces which not just limited transfer bandwidth, but weren't as electrically efficient because the power sipping SATA and SATA 3.0 Gpbs standards that saturate the market today. The interface is really a key performance factor of all laptop hard disk drives because it is a measure from the maximum amount of data that can be transferred to and in the drive. As the interface standards for laptop hard disk drives has kept well in front of their sustained performance potential, it's not uncommon for that interface to become a limiting factor for transfer performance in quick bursts.
Another performance characteristic, often regarded as the main factor influencing overall read/write speed as well as access time is the rotation velocity. Laptop hard drives have power and thermal constraints that limit their performance to spindles with speeds of 7200 rotations per minute (RPM) or less. The faster confirmed disk can rotate its magnetic platter(s), the faster it can write information in addition to find and read stored data. Even at 7200 rpm, the performance of laptop hard disk drives does not compare well to that of similar capacity desktop units.
One of the major causes of this is actually the quantity of platters is limited through the physical height from the drive. Magnetic platters that store data in almost any hard disk require a specific amount of space together in order for a read/write head to move across them and make, change, or access information. Laptop hard disk drives are physically smaller, and thus the quantity of platters is restricted, but same with the performance per platter. Take any two spinning circles of various sizes and something will observe that when rotating the same number of times within the same period, the outer edges of the larger circle will travel a larger total distance. In the realm of laptop hard disk drives which means that the length a read/write covers at 7200 rpm is quantifiably less than the distance it would cover if the platter were physically larger.
The platters themselves also play a factor. The more densely packed the information, referred to as the aural density, the faster it can generally be read from and the quicker it can be written. This isn't always true, as sometimes we've got the technology for the read/write heads lags behinds and an increase in aural density results in slower seek times.
The ultimate performance related factor for laptop hard drives is the cache. The cache is a small pool of volatile memory much like system RAM that provides a buffer for writes and often stores recently and/or frequently accessed information. The buffer may be the primary reason why interface standards can limit bursting performance despite the insufficient sustainable performance approaching theoretical limits of the interface specification.