Data Access Speeds

In order to increase the data transfer rate of a hard drive, the manufacturers provide a number of performance enhancing alternatives to the standard product.

Hard Drive Rotation Speed

The single most important feature is the rotation of the hard drive. The faster the disk spins, the quicker the data can be read or written. Mobile hard drives (2.5" drives) typically run at 4200RPM. To increase the performance, the standard has now been raised so that the average drive runs at 5400RPM. Very high end mobile hard drives run at a staggering 7200RPM, but with a price tag to match! Desktop hard drive (3.5") units average 7200RPM, with some higher end SATA units breaking the 10000RPM barrier. Server based hard disks, with SCSI connections run at up to 15000RPM, but these are specialised server based units, costing the price of a small island.

Buffer Features

An additional trick that is used to eek out the maximum performance on a hard drive is the buffer. A buffer is a bit of RAM (Random Access Memory) which resides on the hard drive, storing the most commonly used information. Data can be written to the RAM much faster than the hard drive, so the more RAM you have, the faster the data access will be. Mobile hard drives are shipped with either 2MB or 8MB of RAM. Desktop drives are shipped with either 8MB or 16MB RAM.

As we supply mainly external hard drives, we find that the rotation speed has more of an impact on performance than the amount of RAM. This is because the 'bottleneck' of the USB or FireWire lead reduces the impact that the extra RAM would have on disk performance.