The Internals

TerraMaster has opted for an unusual feature with the D8 Hybrid, although it's their second device to offer such a functionality and that is the option of adding up to four M.2 NVMe drives to the DAS. This requires the right-hand side to be popped off the unit to access the main PCB of the D8 Hybrid. This is done by removing a pair of screws at the rear of the unit and sliding the right-hand side of the housing forward.


This will reveal a blue PCB which can house up to four M.2 NVMe drives as mentioned. Only 2280 drives are natively supported and shorter drives would require mechanical adapters to fit.


The main PCB also connects to a secondary PCB via a PCIe x4 slot and the secondary PCB is home to the SATA connectors for the four SATA drives. As the D8 Hybrid offered easy access to the main PCB, we decided to pop it out and have a closer look.


There are two main chips on the PCB, the first being four Realtek RTL9210CN USB 3.2 Gen 2 to PCIe Gen 3 x2 bridge chips and the second being two Realtek RTS5432 USB 3.2 Gen 2 4-port USB hubs. The hubs are daisy-chained, with the first USB hub connecting to USB to SATA bridge chips on the secondary PCB, as well as to the secondary USB hub, which in turn connects to the USB to PCIe bridge chips.


If you've counted correctly, that means that only a total of seven USB attached SCSI mass storage devices can be connected between the two hubs, yet the D8 Hybrid supports eight drives. However, as it turns out, TerraMaster has used two different USB to SATA bridge chips, namely a pair of ASMedia ASM235CM and one ASM1352R, with the latter being what gives the D8 Hybrid RAID support. The ASM1352R supports two SATA devices and has an integrated MCU which is what enables the first two SATA drives in the D8 Hybrid to function in the various RAID configurations. This is also why more advanced RAID modes are missing.


While on the topic of the internals of the D8 Hybrid, we have to point out a bit of a glaring issue. If you have SSDs with heatsinks, then the D8 Hybrid isn't for you, as anything taller than the one pictured, doesn't fit. There's also a reason why it's in the third slot, as it doesn't fit in the first two slots due to its height. This is partially due to how the plastic was molded on the inside of the right side of the chassis, as the TerraMaster logo takes up a bit of space, but also the ribs that have been made to strengthen the chassis, ends up affecting the SSD heatsink height. The heatsink pictured is not taller than 6 mm, which isn't a particularly tall heatsink for a modern SSD.