Failure to power off a Tempo card before ejecting it may have an unpredictable result for OS X.
You should follow these steps:
1. Unmount any drives attached to the Tempo card by dragging them to the Eject icon in the dock.
2. Click the Card's icon in the menu bar and select "Power Off Card" from the drop down menu.
3. Push and release the Tempo card to eject.
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