Complex sentence: The Western Digital Raptor (often marketed as WD Raptor) is an upmarket, enterprise-class hard disk drive series produced by Western Digital that created its own niche in the enthusiast, workstation and small-server market.
Split into simpler sentences: The Western Digital Raptor (often marketed as WD Raptor) is a series of high performance hard disk drives produced by Western Digital. The drive currently occupies a niche in the enthusiast, workstation and small-server market.