The title basically says it all. The HP whitepapers simply list Mixed-Use as a general category, but under server quickspecs for most newer HP hardware, Mixed-Use-1 and Mixed-Use-3 options are available (for example, 822559-B21, and 846434-B21 - both are 800GB enterprise SAS 12g SSDs, the sole difference seems to be the 1 or 3).
What does the mixed use number indicate?