In reply to a post by jchamier:

Everything on a modern HDD or SSD is virtual, known as "Logical Block Addressing". The operating system makes a request for an LBA and gets the data returned. It has no connection to any physical arrangement.

And it gets further and further away from a 1:1 mapping with each new approach to hard drive tech.

For example we now have drives that have multiple different levels of storage density on the same disk. They have a small area of low density, high speed storage and then most of the drive is higher density, lower speed.

The high speed area is used as cache, to write quickly to and the drive firmware will move data to the slower high density areas when it needs to. The drive may also have a separate SSD like flash memory area, for further caching data to improve speeds (basically to hide the slow speed of the high density storage area).

Some SSDs take a similar approach.