Sector Leaders were mostly higher Wednesday, with volume performances quite mixed. Three leaders logged heavy volume. The big volume winner of the day was data backup and retrieval company CommVault Systems (CVLT), which rose 0.95 to 76.83. But volume soared to 10 times its usual pace. That surge can be traced to CommVault's shift to the midcap S&P 400 index from the small-cap S&P 600. CommVault has risen 10% from its 70.02 buy point from a rare