Perhaps adding ARC is similar to, but not the same as OS level file system cache. And explain the difference in straight forward wording.
Plus, after the ARC section, perhaps adding a L2ARC paragraph.
Then add a section on Special Metadata vDevs.
Last mention De-duplication. My suggestion here would be to state if you don't know how to design and implement, so that you have to ask beginner questions, then you should NOT be using De-duplication.
I am not saying these new sections should be all encompassing, but adding the general description and pointers to more detailed information, I would think would be help full.
As a total noob, I appreciate the effort and am very grateful for the clarity. I didn't feel it deserves 5 stars because the title is misleading; it suggests much broader coverage than just RAID terms.