How hard drives work @ Icrontic.com

[Wizno]

SSDs feature very fast burst read/write speeds, which are periods of
disk activity that are much faster than normal due to data being
physically close and easy to recover. On the other hand, they are
slower than today's hard drives for writing sequential clusters of
information, a process known as sequential writes.


http://icrontic.com/articles/how_hard_drives_work