HP Mini G2 Through G9: What Changed, and What It Means for Racking

The HP Mini is the most common thing I see people rack that was never meant to be racked. It is cheap on the secondhand market, it idles at single-digit watts, it has a real vPro-capable CPU in a lot of configurations, and it is about the size of a hardcover book. Buy three of them off a lease-return seller and you have a Proxmox cluster for less than the cost of one new 1U server chassis.

The catch is that "HP Mini" is not one product. It is roughly a decade of machines sold under EliteDesk, ProDesk, Elite Mini, and Pro Mini names, across generations labelled G2 through G9, and the chassis did not stay still the whole time. It changed meaningfully once, drifted slightly a second time, and then got renamed in a way that makes the part numbers look far more different than the hardware actually is. If you are buying a mount for a machine you have not physically measured yet, that history matters.

The mount for this build:

10" HP Elite/ProDesk Mini G3 G4 G5 G6 G9 Rack Mount 1U

The short version: two chassis families, one rename

If you want the answer without the archaeology, here it is. The G2 is its own thing and needs its own mount. Everything from G3 forward — G3, G4, G5, G6, and the G9 machines HP now calls Elite Mini and Pro Mini — shares a close enough external envelope that a single mount handles the lot. That is why the catalog splits exactly there and not anywhere else.

The reason is mechanical, not marketing. A rack mount for a device this size does not care what CPU is inside it. It cares about three things: the outside dimensions of the box, where the vents are, and where the ports and the power jack come out. The G2 differs from the G3 on the second and third of those enough that a shared mount would either block airflow or foul a connector. From G3 onward, HP kept the footprint stable through several silicon generations, which is unusual and, for our purposes, convenient.

What actually changed between G2 and G3

The G2 generation sat on the Skylake-era platform and carried HP's older small-form-factor design language: a slightly different side vent pattern, a rear I/O cluster laid out for the VGA-and-DisplayPort era, and a flex-port bay positioned differently from what came later. The chassis is close to the same size — call it roughly 175 mm on the long dimension and around 35 mm thick lying flat — but "close to the same size" is not the same as interchangeable when you are cutting a mount to a tolerance that keeps the machine from rattling.

Two practical consequences. First, if you have a G2 and you try to seat it in a G3-onward mount, the fit will be sloppy in some axes and tight in others, and the rear cutout will not line up with your ports. Second, the intake path is not in the same place, so a mount designed around one generation's vent layout can end up shadowing the other's. Neither failure is dramatic — the machine will not melt — but you will see higher steady-state temperatures and you will hear the blower more, which defeats most of the reason people rack these things in the first place.

So: G2 gets the HP EliteDesk/ProDesk Mini G2 10" Rack Mount - 1U in a 10-inch cabinet, or the 19" HP EliteDesk/ProDesk Mini G2 Rack Mount - 1U (Modular) if you are in a full-width rack. Do not try to make the later mount work. I have had people ask.

G3, G4, G5: the stable middle

This is the sweet spot of the used market right now, and it is also the easiest group to plan around. G3 through G5 span Kaby Lake through Comet Lake, roughly 7th through 10th generation Intel, and HP left the enclosure alone across all of it. Same footprint, same vent geometry, same rear cluster arrangement, same external power input. You can mix a G3 and a G5 in the same rack row and they will sit identically.

What varies within the family is internal, and it affects your thermal planning rather than your mounting. The later parts in this range push higher sustained power in the 35W-class configurations, and the 65W-class desktop-CPU variants — the ones with the T-suffix chips — run noticeably warmer under a real load than the U-class machines people are used to. If you are stacking four of these in a closed cabinet, the CPU generation matters more than the chassis generation.

The mount is the same either way. In a 10-inch mini rack, that is the 10" HP Elite/ProDesk Mini G3 G4 G5 G6 G9 Rack Mount 1U; in a 19-inch rack, the 19" HP Elite/ProDesk Mini G3 G4 G5 G6 G9 Rack Mount 1U (Modular). The 19-inch version is modular, which matters more than it sounds like it should — see below.

G6 and G9: new names, familiar box

Here is where the part numbers get confusing. HP retired the EliteDesk and ProDesk Mini names and replaced them with Elite Mini 800 and Pro Mini 400 at the G9 generation. Different branding, different marketing photography, different spec sheet layout. The box itself stayed within the envelope the mount was already cut for.

The gotcha is on the power side, not the mechanical side. The higher-end G9 configurations ship with larger external adapters than the 65W units most G3-through-G5 machines came with, and the barrel is not always the same physical connector across the range. If you are consolidating a mixed fleet and assuming you can pool spare power supplies, check the actual adapters before you plan on it. Nothing is more annoying than discovering at rack-up time that the third node's brick does not match the other two.

The second thing to check on G9 is the front port layout. Some SKUs put USB-C up front, some do not, and if you were counting on front-panel USB-C for a KVM dongle or a config cable, verify it on the machine you actually bought rather than on the family spec sheet.

Power, heat, and what 1U really costs you

A 1U opening in an EIA-310-D rack is 44.45 mm of vertical space. An HP Mini lying flat is comfortably under that, which is the whole trick: the machine goes on its side, not standing on its stock foot, and you get a full node per rack unit with room left for air.

Three things to plan for:

• Exhaust direction. These are single-blower designs that pull from the side and bottom and push out the back. Racked flat, the intake ends up facing the adjacent rack unit. Leave a vented blank or a deliberate air gap above a node that runs hot, rather than sandwiching four of them in a solid column.
• The power brick. Nobody puts the adapter in the plan and then everybody has to find somewhere for it. A 65W HP adapter is a brick roughly the size of a deck of cards plus its cable strain relief. In a 10-inch cabinet, that is real estate you do not have. Decide up front whether the bricks live on a shelf, cable-tied to a rear post, or outside the cabinet entirely.
• Barrel jack strain. The DC input is a barrel connector on a plastic-bodied jack, not a locking connector. If the adapter cable hangs unsupported, its weight works on that jack every time something vibrates. Tie the cable off within 150 mm of the machine.

On noise: the blower in these is not loud at idle, but it is a small high-RPM fan, so when it does spin up it makes a thin whine rather than a broad whoosh. In a closet, one node is fine. Four nodes all stepping up together at 2 a.m. during a backup window is a different experience. Thermal headroom is the cheapest noise mitigation available.

Planning a mixed-generation rack

Most people do not buy three identical machines. They buy whatever was cheap that month, which means a G4 in January and a G9 in June. That is fine, and it is exactly the case the mount lineup is built around, but a few rules keep it tidy.

Standardize on rack width first, generation second. Decide whether you are in a 10-inch mini rack or a 19-inch rack, because that decision is expensive to reverse and the generation question is not. If you are in a 19-inch rack, the modular 19" HP Elite/ProDesk Mini G3 G4 G5 G6 G9 Rack Mount 1U (Modular) lets you put two devices side by side in one rack unit, which is how you get a four-node cluster into 2U instead of 4U.

Group by thermal load, not by generation. Put the two machines with T-series desktop CPUs at the top of the stack where the warm air is going anyway, and the low-power U-class nodes below them. Generation labels tell you almost nothing about heat; the CPU suffix tells you nearly everything.

Keep one spare mount on hand if you run more than three nodes. Not because they fail — they do not have moving parts — but because the moment you find a fourth machine at a good price you will want to rack it the same day, and waiting a week for shipping is how a node ends up living on top of the switch for three months.

Finally, label the generation on the mount itself, not on the machine. When you pull a node for a memory upgrade, the label stays in the rack and tells you what goes back in that slot. This sounds fussy until the first time you put a G2 back into a G5 position and spend ten minutes wondering why nothing lines up.

Wrap-up

The whole HP Mini generation story reduces to one line: G2 is its own mount, and G3 through G9 share one. Everything else — the renames, the CPU jumps, the port shuffles — changes what the machine can do, not how it sits in a rack. Buy on price and CPU, check the adapter wattage before you standardize on spares, leave air above the hot nodes, and the fleet takes care of itself.

Mounts in this build