10. Given the function $f ( x ) = \left\{ \begin{array} { l } x + \frac { 2 } { x } - 1 , x \geq 1 \\ \lg \left( x ^ { 2 } + 1 \right) , x < 1 \end{array} \right.$ , then $f ( f ( - 3 ) ) =$ $\_\_\_\_$ , and the minimum value of $f ( x )$ is $\_\_\_\_$ .