This first 16 bars of the solo move in and out of the blues scale; from a natural Bm scale to F# dorian. Based mostly around simple pentatonic positions and "box" scales, it portrays Petrucci's ability to take elements of blues/classic rock and combine it with a more technical shred approach to produce a sound quite distinct to John.
Be aware of pick stroke directions as well as legato, as many Petrucci-licks incorporate both to offer a percussive sound similar to that of Paul Gilbert.