superfetch and disk defragmenter ignore SSDs drives. You may leave it on, it will work on hard drives that you have on system.
D1. Win7 x64 i7-3770 on Z77, HD7850, 2707WFP, 840, X-Fi D2. Win7 x64 E8400 on P35
L1. OSX 10.9 rMBP 13 L2. Vista x86 E1505
M. Galaxy S4