When i first tried doing some sweep picking that i saw petrucci do i couldnt do it at all. I wasnt even playing it at 60bpm i was so slow. I was amazed at how fast he was playing it. I was saying to my guitar teacher about how fast petrucci was playing these arpegios. He told me that if i practiced with a metronome i would get better. I never thought i would be able to play anywhere near as fast as he was. I have been playing for just over a year now and last lesson i had i started playing some arpegios while my teacher was tabbing out something for me. He was so impressed he got the other guitar teacher who was also teaching someone at the time to come and watch me. That arpegio above is the best one to start practicing on because its not that hard. Remember that when you sweep pick and arpegio you are playing the notes from a certain chord. Work out the chord the you are sweep picking and see where you are putting your fingers for the chord.