What is the transfer rate between the hard drive and RAM?

Answer 1

An interesting question, that has a spectrum of answers. The speed at which data can be retrieved from a hard disk drive depends on the speed at which the disk itself passes below the head, hence servers have disks that spin at 10,000 or 15,000 rpm. Home computers have slower disks because they're cheaper and laptops typically have disks that are slower still, typically 5400 rpm because the power drain increases with speed as a result of frictional losses. Although it's a critical factor in the perfromance of a hard drive, manufacturers seldom give sensible figures for *sustained* read and write speeds. Instead, they often state the *maximum* speed, however, this is unrelated to data transfer between the physical platter and the read/write head. All disk drives have a limited amount of buffer memory. The *maximum* speed is the rate at which data are transferred in & out of that memory, which is usually limited by the interface. As a result, a maximum speed of 1 Gbyte per second might be listed in a specification, but the *sustained* speed might be more like 50 or 60 Mbytes per second, which sounds much less impressive. It's still a lot more than flash drives though - don't fall for the idea that a solid state laptop will be faster than one with a spinning disk, it won't, at least not yet.