sentences:  Version 1.0 of Varnish was released in 2006, Varnish 2.0 in 2008, Varnish 3.0 in 2011, Varnish 4.0 in 2014, Varnish 5.0 in 2016, and Varnish 6.0 in March 2018.Varnish stores data in virtual memory and leaves the task of deciding what is stored in memory and what gets paged out to disk to the operating system.This helps avoid the situation where the operating system starts caching data while it is moved to disk by the application.