The Quad is a 4 drive model where all 4 drives are used by the RAID controller, the Quad es is just like the Quad plus an additional spare drive located in a 5th bay as a cold spare.
Dulce Systems has engineered a bundled solution using the latest in storage technologies from disk drives to enclosures to RAID controllers to end user applications, all working together to address reliability, features and performance at a budget-minded price. Ultimate bottom line: the stuff works in your applications. We confidently stand behind that with the industry’s longest warranty of 42 months!