After recognizing that my drobo failed due to a problem (…a known problem at seagate…) I googled around and found that the problem will get worse on time.
Users reported that their drives (Barracuda 7200.11, 1TB cap. – Model …340AS) have been locked down after a while and they couldn’t get out data because the drives even won’t be recognized any more on BIOS level…
Yesterday I downloaded the firmware update for the drive – but have to organize an external SATA dock to upgrade. DROBO is not useable to update the firmware of drives…
… today the support page at seagate vanished… only a dead link remains on their knowledge page.
A friend of mine, told me he also had the problem with the drive and got an exchange via Seagate Munich – so maybe this would be the way I’ll go now.
Another friend of mine also has troubles with his drobo which are related to a Seagate drive out of this series…

Update
Seems that they have a problem with the knowledge-DB at seagate. All links are not working…

Storage drive, Drobo, Error