Comay BladeDrive Design
The Comay BladeDrive E28 sports an impressive profile. The SSD comes in a full-height 3/4-length PCIe form factor. The SSD we evaluated is a pre-production model, but we noted some bowing in the center of the card. The thermal pads employed between the two PCBs were a bit too thick, but this will likely be addressed in production runs. We can see the tiered design of the card with four layers of components. A large heat sink covers the top of the card, shedding heat into the server chassis.
A large rear covering doubles as the baseplate for the drive. The perforated rear bracket facilitates the required 300LFM airflow.
Four large thermal pads stretch the length of the bottom of the heat sink to cool the uppermost four rows of NAND. A smaller heat sink to the left covers the RAID controller.
Peeling the SSD apart reveals two connectors that mate the PCBs together. Sixty-four Toshiba 19nm MLC NAND packages line this side of the PCBs.
An additional 64 NAND packages line the rear of the PCBs for a total of 128 TSOP NAND emplacements on the BladeDrive. Each NAND package holds 16GB. This gives the SSD 2,048GiB of RAW NAND. The PCBs also provides mount points, hidden under the NAND die, for BGA packaged NAND.
Eight SF-2581 controllers are spread amongst the PCBs, with each controlling 16 NAND packages. Each SSD controller handles 256GB of RAW NAND, 200GB of which is user-addressable. The remaining capacity of each SSD is split between overprovisioning and RAISE functionality (Redundant Array of Independent Silicon Elements). RAISE provides RAID 5-like redundancy to each individual bank of NAND controlled by the SF-2581 controllers. These SSDs are configured in RAID 0 for optimum performance and maximum capacity.
The Comay SBC208-2 controller aggregates the eight SF-2581 controllers and presents them to the operating system as one large striped volume. The SBC208 controller is an 8-channel proprietary RAID controller that is developed and used exclusively for the BladeDrive PCIe SSD. To the bottom right, we notice two supercapacitors that provide enough power to flush the data to the NAND in the event of power loss. SandForce SSDs do not require DRAM. This provides them an inherent advantage in power-loss scenarios.
Comay BladeDrive Specifications
The Comay BladeDrive E28 supports Windows Server 2012 and 2008, along with all major Linux distributions. The unrecoverable bit error rate is less than 1 sector per 10^16 bits read. DuraWrite provides compression capabilities to minimize NAND wear, and intelligent global dynamic and static wear-leveling also enhances flash life.