Macintosh bootable volumes are supported on the internal 2-port PCI card (part number TSATA) but are not supported on any of the other SATA cards at this time.
Using a Drobo S with a Macintosh and Sonnet Tempo SATA E2P, Tempo SATA ExpressCard/34, or Tempo SATA Edge ExpressCard/34. you may get a device removal error after waking up from sleep. The Drobo S will automatically reconnect. System caches are flushed before sleep, so there is not data loss.