Installing Hard Disks And SSDs
The Obsidian 900D sports a total of nine 3.5” bays. Drives are inserted from left to right, and thus sit perpendicular to the case. The uppermost cage can be removed and mounted below the external 5.25” bays or installed at the bottom of the case, in front of the power supply.
The caddies are made of plastic, and they allow tool-less drive installation. Locking or unlocking a loaded caddy into a cage is achieved with a lever that seems to work reliably (though empty trays are somewhat flimsy).
Each caddy sports rubber grommets that decouple mechanical disks from the tray, while holding the drive in place with a metal pin. The grommets do their job; my microphone didn't pick up any major vibration or audible resonance from the identical 1 TB Samsung Spinpoint F3s I used for testing.
In order to mount a hard disk in the tray, each of the caddy’s side rails needs to be bent slightly, allowing you to slide the locking pins into the drive's mounting holes.
Installing SSDs or 2.5” Hard Disks
SSDs and 2.5” hard disks are too small to work with the locking pins. Instead, they have to be mounted to the bottom of each tray using four M3 screws. In this way, SSDs and mechanical drives can be mixed and matched inside the Obsidian 900D. When I'm working with lighter aluminum cases, I typically mount heavy disks near the bottom for a lower center of gravity. But in the case of Corsair's big flagship, you can really put them wherever you want.
SATA Hot-Swap Bays
Hidden behind the lower lid are six fixed 3.5” drive bays. The three on the right are set up as hot-swappable SATA bays. They accommodate the aforementioned plastic trays, and upon insertion, engage with a factory-mounted SATA port. The power pins in the backplane all connect to a single SATA-style power plug.