Originally Posted by purenuman

The cache doesn't help unless you ask for the same data again.

When a hard drive is accessed, the data is copied from the drive to the cache and then delivered to the calling process.
This is done so that the next time that data needs to be accessed it can be taken straight from the cache, reducing the access time because the platters themselves will not need to be accessed.
It only speeds things up if you are calling the same data over and over....