1GB cached mechanical hard drive is it just a few seconds faster when copying files?

Problem: "The cache is 1GB, even if the write speed peak 400mb,2.5 seconds cache is light, but the hard disk write speed will not be higher than 100MB, even if 3 seconds, also even if only 3 seconds, below the turtle speed, is this mean?"

Answer: In reality, there are few situations where you write at 400MBps for a long time. Imagine how many times a week you write more than 1GB of data to a mobile drive?

In fact, caching is based on the local principle of program execution and data access. It is assumed that within a certain period of time, a program executes code and access to the data are within a certain region. In this way, the data that needs to be reused during this time (the code is also a kind of data, although it can be handled separately, but the same principle) can be obtained directly from the cache without having to access slower storage devices, thus shortening the time to improve efficiency.

Indeed, if you copy a 50GB movie, the cache does not make much sense: Because the 50GB data is completely non-localized.