A photographer’s Drobo showing two amber bays at once. BeyondRAID is proprietary and undocumented, so no standard tool reads it — and that, rather than the two failed disks, is the actual difficulty.
This is a scenario, not a case study. It describes a failure pattern we handle regularly and how it is approached, written from the technical work rather than from one client's job. Our documented case files are here.
A proprietary array — Drobo's BeyondRAID being the best known — stops presenting its volume, or the chassis itself fails. Unlike a standard NAS, the disks cannot simply be read on other hardware, because the layout is not one any standard tool understands.
Proprietary arrays offer genuine advantages: mixed disk sizes, capacity added without rebuilding, redundancy adjusted on the fly. Delivering that requires abandoning fixed stripe geometry in favour of a block allocation map that records where every chunk of data physically sits.
That map is the array. Without it the disks hold data in an arrangement with no discoverable regularity — there is no stripe order to derive because there is no stripe order.
The consequence is dependence on the vendor's implementation. Where a standard mdadm array can be assembled on any Linux machine, these can only be read by the original hardware or by a laboratory that has reverse-engineered the format.
On a standard NAS a dead chassis is an inconvenience: put the disks in any other machine and read them. On a proprietary array it can be the whole problem, and where the manufacturer no longer exists or no longer supplies replacements, a working chassis may be genuinely unobtainable.
Which is why these arrive here more often than their market share suggests. The disks are frequently healthy and the route to them has closed.
Recovery means parsing the allocation map from the disks directly and reassembling the volume from the images according to it — work that depends on knowing the format rather than on any general technique.
The chassis dependence adds a failure mode standard arrays do not have. Redundancy inside the unit does nothing about the unit itself.
The allocation map is distributed across members. A partial set is frequently not reconstructable, and bay order still matters for parsing it.