Orthogonal similarity transformation

Can someone please show me how to diagonalize a matrix such as the one below using an orthogonal similarity transformation? $$\begin{bmatrix} 2 & 1 & 1 \\ 1 & 2 & 1 \\ 1 & 1 & 2 \\ \end{bmatrix}$$

I have been looking everywhere online to find an example of orthogonal similarity transformations but I can't find any. Am I searching for the wrong thing? Is there another name for it, because similarity transformations seem awfully close to Jordan canonical form?

For stuff like that WolframAlpha is a great help: $$\pmatrix{2&1&1\\1&2&1\\1&1&2}=SDS^{-1}= \pmatrix{ -1&-1&1\\ 0&1&1\\ 1&0&1 } \pmatrix{ 1&0&0\\ 0&1&0\\ 0&0&4 } \frac13 \pmatrix{ -1&-1&2\\ -1&2&-1\\ 1&1&1 }$$