In the ancient times of databases we had to make sure that we wrote to 'raw' disk devices bypassing any possibility of the operating system file caching/bufferi

In the ancient times of databases we had to make sure that we wrote to 'raw' disk devices bypassing any possibility of the operating system file caching/buffering failing to 'flush' our writes all the way to the disk. There was an implied guarantee that what we thought we wrote was actually written to disk. In today's world of 'virtual' everything which may sometimes be many levels removed from the raw disk devices, how do we still ensure that a write to a database is still a write to a physical device as opposed to an incomplete write that looks like a completed write to a higher level virtual disk? Is there a guarantee that everything is flushed to a physical disk?