On 11 Dec 2015, at 8:29am, ??? <2004wqg2008 at 163.com> wrote: > 1.Reboot computer > 2.Shut down computer ,and then start computer
I am sorry to say that ??? (copy and paste, I don't know Chinese !) has given the first correct answer. There are at least three levels of caching involved in fetching data from disk, and there is no way to tell the computer to flush all of the levels. Testing different options for disk speed can only be done by either 1) Using a huge amount of data which is bigger than any cache you may have (at least 4 gigabytes on a standard setup) 2) Turning the computer off and on again Simon.
