Sonnet has tested the following cards with the Drobo S:
Tempo SATA E2P..............................compatible
Tempo SATA E4P..............................not compatible
Tempo SATA ExpressCard/34...........compatible
Tempo SATA Edge ExpressCard/34...compatible
Tempo SATA Pro ExpressCard/34.....not compatible
Tempo SATA X4P..............................not compatible
Qio eSATA ports...............................not compatible
Sonnet has isolated the occurance of drives not mounting in 10.7.4, which occurs only in 32-bit mode with the Tempo SATA E4P, E4i, and Tempo SATA Pro ExpressCard/34. Users running in 64-bit mode will not experience any issue. (To boot in 64-bit, hold down the 6 and 4 keys when the Mac starts up.) Install driver 2.2.9 or greater to fix the 32-bit mode issue.