Thanks for this info.
Drobo is a RAID device, and is shipped with a Drobo dashboard, which is the interface that controls the creation of the volumes on the Drobo RAID (and perhaps the initializing of the volumes) and also serves as the driver for OS X. I don't know the details because I do not own one of those. I have participated in a few online presentation for the Drobo devices and have seen demos of how the Drobo dashboard functions. On the Drobo devices without Ethernet interfaces (such as Drobo 5D / Drobo Mini), the communication with the Drobo is done via another port (USB and perhaps Thunderbolt) for the purposes of configuring the Drobo device. Drobo dashboard exists as a Windows and Mac application. On the Drobo devices that can serve as an iSCSI target, the Drobo dashboard also includes an iSCSI initiator for OS X, but this does not apply to Drobo 5D / Drobo Mini.
So, you are probably correct that there must be a driver in ESXi to be able to communicate with the Drobo RAID controller. On the other hand, I believe that the volume initialization and management can be done with a Windows or OS X client, so that piece of the Drobo dashboard functionality does not have to be present in the ESXi driver. So, the volume could be initialized with a Windows or OS X laptop/desktop, and once it's created, the Drobo should be able to be connected to the ESXi 5.x running on the Mac Mini and ESXi should be able to see the volume created earlier and format it with its own file system. The problem, as you correctly pointed out, is the fact that ESXi has no driver that can communicate with the Drobo RAID controller in order to see the volume that's created on the Drobo 5D / Drobo Mini.
I can try to contact someone within Drobo to see if they would be interested in the open source community creating a driver for their Thunderbolt devices to be used with ESXi. I don't know if I will get anywhere with it.
Provided that the creation of such a driver could be possible, Drobo 5D / Drobo Mini would provide the best solution for redundant datastore with ESXi running on Mac Mini. No one would be able to beat the storage capacity, expandability, storage bandwidth with any other (non-Thunderbolt) device for the price of Drobo Mini or Drobo 5D. Drobo Mini is also extremely quiet, so you could set it side by side with the Mac Mini right on your desk and not be bothered by excessive fan noise, so this is a perfect solution for a home lab. With most NAS devices, you really have to put the NAS in a closet or another room so that the noise does not bother you. And because most closets are not air-conditioned, it's always a problem to find the right location for a noisy NAS.
With the Mac Mini running ESXi and having the datastore on a Drobo Mini, there's really no need for a NAS because the OS X Server app provides all functionality that a consumer-grade NAS does and then some, and the Thunderbolt Drobo would provide data storage redundancy.
Thanks again!
