This technical teardown and build report details the engineering of a custom high-density 45-bay JBOD (Just a Bunch of Disks) storage enclosure, capable of exceeding 1 petabyte of raw capacity using 24TB enterprise HDDs. The project transitions from standard consumer NAS solutions to a purpose-built, rack-mountable chassis featuring a G90 galvanized steel frame and over 30 custom-designed PCBs.
The architecture utilizes a dual SFX power supply configuration to meet the high 5V/12V current demands of 45 mechanical drives, managed via a custom-coded microcontroller for power sequencing and thermal control. Data connectivity is established through dual SAS expanders and 12 custom-manufactured backplanes, featuring impedance-matched high-speed differential pairs. A significant portion of the development was dedicated to "automated side quests," including the creation of hardware-in-the-loop (HIL) testing boards to verify PCB continuity and voltage accuracy before integration. Final validation includes ZFS RAID-Z2 performance benchmarks and real-time vibration analysis via onboard accelerometers to ensure long-term mechanical reliability of the drive array.
0:00 High-Density Storage Design: The system is engineered to house 45 enterprise-grade 3.5-inch hard drives (e.g., Western Digital HC 550) within a compact, vertically optimized rack-mount enclosure, achieving over 1PB raw capacity using 24TB units.
3:50 Structural Foundation: The chassis utilizes laser-cut G90 zinc-plated steel for structural rigidity, supporting a ~30kg load. Integration includes press-fit nuts and 3D-printed components with copper heat-set inserts for component mounting.
5:50 Power Distribution Strategy: To overcome the limited 5V rails on consumer SFX power supplies, the build employs two non-redundant PSUs. The drive array is split into two power groups to safely handle peak spin-up currents (staggered spin-up is also utilized).
7:19 High-Speed Backplane Engineering: Data integrity is maintained via 12 custom backplanes featuring 100-ohm impedance-matched traces and length-matched pairs to support 12Gb/s SAS signaling. Connectors include Mini-SAS HD (SFF-8643) interfaces.
10:09 Automated Hardware Validation: To mitigate the risk of "catastrophic short-circuiting," custom testing boards and CLI software were developed to automate resistance and continuity checks across 1,000+ solder points prior to drive installation.
10:50 Electronics Stack & SAS Expansion: The system uses two modified SAS expanders to route data from the host HBA (Host Bus Adapter) to the backplanes. A custom "mini-motherboard" manages PSU power states via USB commands and controls Noctua fan PWM curves for silent operation.
13:40 Custom Loom & Power Verification: Over 20 meters of custom-crimped and heat-shrink-labeled wiring provide dedicated power lines for each backplane. A relay-based testing jig was built to verify 12V/5V polarity and voltage levels before the system was energized.
17:55 Thermal & Vibration Management: 3D-printed disk retainers and floor panels force airflow specifically between drives. Integrated LED strips provide per-bay health status. Vibration is minimized through plastic geometry optimization to prevent mechanical wear.
21:46 I/O Performance & Bottlenecks: While the SAS fabric supports ~96 Gb/s, the system is bottlenecked by the host PCIe 3.0 x8 link (64 Gb/s). Sequential read tests approached saturation of the PCIe bus, while writes were limited by the test bench's CPU overhead for parity calculations.
23:09 ZFS Architecture: The array is configured using ZFS RAID-Z2 across sub-pools of six to seven disks, providing a two-disk failure tolerance per pool and roughly 540TB of usable redundant storage from 810TB raw.
25:18 Mechanical Stability Verification: Accelerometer-based vibration analysis confirmed RMS acceleration levels of ~0.02-0.03 Gs during operation. This is significantly below the 0.2 G performance degradation threshold and the 0.67 G hardware error limit specified by drive manufacturers.