How to rack a two-node GB10 / DGX Spark cluster

Two GB10 machines linked over ConnectX-7 give you a small two-node cluster. That's useful for models too large for one box's 128 GB of memory, or for testing distributed jobs before they go to real hardware. Physically, though, it's two warm boxes, two external power bricks and a short, stiff cable that has to run between the rear ports. This guide covers how to fit all of it into one 2U rack space so it stays cool and the cable doesn't get bent too tightly.

We use our 19" 2U dual GB10 mount for the assembly steps, but the spacing, cable and power advice applies to any rack setup.

Plan the space before you start

Rack units

Each GB10 box is 50.5–54.5 mm tall depending on the brand, and one rack unit is 44.45 mm, so the pair needs 2U. Reserve a third unit above or below if you can. A vented blank there keeps a neighboring device's exhaust off the cluster and gives your hand room to reach the rear ports.

Side-by-side spacing

Don't push the two boxes against each other. Each one sheds heat through its sides as well as front to back, and two warm walls touching just trap it. Our dual mount leaves a 40 mm vented gap with a vented centre spine and vented inner walls, so air keeps moving between the units. The gap also gives the ConnectX-7 cable room to make its turn. If your rack runs hot or you're using a thicker cable, the generator can design the same mount with a gap of up to 120 mm.

Depth

The boxes are about 150 mm deep, which is shallow by rack standards. Most of the depth you need goes to the cables behind them: a QSFP plug plus its bend, the USB-C power leads, and Ethernet. Allow at least 100 mm behind the rear face of the units before any door or wall.

ConnectX-7 cable routing

Every GB10 machine has two QSFP ports for its ConnectX-7 network adapter. For a two-node cluster, you connect one port on each unit with a direct-attach cable (DAC). Check NVIDIA's documentation for supported cables. In practice, people use short passive copper DACs because the units sit right next to each other.

• Use the shortest cable that reaches without strain. In a side-by-side mount that's usually well under a metre. Extra length has to be coiled somewhere, and coiled DAC acts like a spring.
• Respect the bend radius. DAC cable is thick and stiff. Let it leave the port straight, then curve it gently through the gap between the units rather than doubling it back on itself.
• Route it through the gap, not over the top. The 40 mm channel between the pockets is there for this. Cable laid across the tops of the boxes blocks the airflow above them.
• Strain-relieve it. Use a loose zip tie or hook-and-loop strap through the slots in the mount floor so the cable's weight doesn't hang off the port.
• Label both ends. If you later add a switch, you'll want to know which port is which without pulling the boxes.

Power bricks: the part people forget

Each GB10 unit takes an external USB-C power brick (240 W on the DGX Spark). Two bricks loose on the rack floor, sitting in exhaust air, is a common way to cook them. Better options:

• Put them on a shelf at the rear of the rack, outside the exhaust stream of the cluster.
• Strap them to the rear rails with hook-and-loop straps, so they hang in free air.
• Plug both into a PDU or UPS outlet you can switch off, so you can power-cycle the cluster without reaching behind it.

Keep the USB-C power leads separate from the QSFP cable where you can. That's for tidiness and access; the power leads won't cause interference.

Airflow checklist

• Front of both units open to room air: no solid door panel directly in front of them.
• Rear of both units clear: no cable bundle pressed against the exhaust.
• Nothing hot directly under the mount. If a switch or server sits there, put a vented 1U between them.
• A warm closet or an enclosed rack? Order the mount in ASA rather than PETG (see materials), and think about a 19" fan panel to move air through the enclosure.

Step-by-step: installing our dual 2U mount

The dual mount is wider than our print bed, so it prints as two halves. They slide together on a tongue-and-groove seam and clamp with three M4 through-bolts across the centre spine. The nuts sit in printed captive pockets, so you only turn the bolts from one side, using a 2.5 mm hex key.

1. Dry-fit the halves. Lay both halves face-down on a table and slide the tongue into the groove. They should meet flush along the faceplate without forcing. Don't seat the bolts yet.
2. Drop in the nuts. Press an M4 nut into each of the three hex pockets in the centre spine. They're shaped so the nut can't turn. A dab of tape over each one stops it falling out while you work.
3. Bolt the spine. From the other side, push the three M4 bolts through and tighten them with the 2.5 mm hex key until the seam closes. Snug is enough. Over-tightening plastic crushes the spine and adds nothing.
4. Check the faceplate. Lay a straightedge across the front. If the halves are visibly out of line, loosen the bolts, reseat the tongue and tighten again.
5. Fit cage nuts in the rack. Put cage nuts (or clip nuts) in the rail holes for your two rack units. Most racks take M6 or 10-32 screws; use your rack's own hardware.
6. Mount it empty. Lift the mount into the rack and fit the four rack screws by hand, then tighten. The mount is light on its own, so this is the easy moment to get it level.
7. Seat the units. Slide each GB10 into its pocket from the front, ports facing the rear. Feed a zip tie through the floor slots and over each unit to hold it in place. Snug, not tight.
8. Connect the cluster cable. Plug the QSFP DAC into one ConnectX-7 port on each unit, routing it through the gap. Strain-relieve it to the floor slots.
9. Power and network. Connect the USB-C power from the bricks and Ethernet to each unit, dress the cables to the side, and power on.

If anything doesn't fit the listed device, send us a photo within 30 days and we'll reprint it free. That's our catalog fit guarantee.

When to choose a different layout

Choosing a different gap, three units, or a 10-inch rack? See our 10" 2U GB10 mount for single units in mini racks, or design a custom layout in the rack-mount generator. For the full comparison of printed and steel options, read “NVIDIA DGX Spark & GB10 rack mounts: every option compared”, and the GB10 hub lists every model we've sized.

FAQ

Do I need a switch to cluster two GB10 units?

Not for two. A single QSFP direct-attach cable between one ConnectX-7 port on each unit is enough. A switch becomes relevant if you grow past two nodes.

Can I stack two single mounts instead of using a dual?

Yes, it takes 4U and puts one unit in the other's rising heat, so add a vented 1U between them. The dual keeps both in 2U with a dedicated gap for the cable.

Are the bolts hard to reach once it's in the rack?

Assemble the halves before mounting. The bolts tighten from one side only, so you won't need to get behind the spine once the mount is installed.