10GbE at Home: The Bottleneck Is Almost Never the Network

By LK Wood IV · Published 2026-09-07 · ~8 min read · St. Louis County, MO

Ten gigabits per second is 1.25 GB/s on the wire. A single Seagate Exos X24 is rated at 285 MB/s at its outer tracks, and that is Seagate’s own best case rather than what you will see.

That gap is the article. The fans, the cables and the cards are all real problems, and I will get to each of them, but none of them is the reason your transfers are slow.

The fan is the first thing you notice and the first thing you fix

Fan noise is what you will register in the first hour of owning a 10GbE switch, and it is what you will deal with first. There is an aftermarket in quiet replacement fans for these switches, and it exists because everyone who buys one hits the same wall in the same week.

The swap works. I do not treat it as a compromise or as a mod you put up with — a fan specified for a datacenter row is the wrong part for a shelf in a room where someone sits, and replacing it is the correct configuration for where the switch actually lives.

If you have not bought yet, there is a shorter path: buy a switch that never had a fan. MikroTik lists cooling type Passive for both the CRS305-1G-4S+IN, with four SFP+ ports, and the CRS309-1G-8S+IN, with eight. Four 10G ports covers a NAS, a workstation and a hypervisor with one spare, which is most houses.

DAC under five meters, fiber past that

Passive DAC for short runs. It is cheaper, it runs cooler, it draws less, and there are fewer parts in the path that can fail.

Cisco’s 10GBASE SFP+ datasheet puts a number on “short.” Its passive Twinax cables are listed at 1, 1.5, 2, 2.5, 3, 4 and 5 meters; active Twinax starts at 7. Five meters is where the industry draws the line.

The power figures in the same document: 0.1W for a passive Twinax cable, 1W for an SFP-10G-SR module — and an optical link needs two of those modules, one at each end. Ten times the draw per port, plus two components that can fail independently of the cable between them. Inside a rack or across a room, take the DAC. Through a wall or across a house, take fiber and accept the transceivers.

The bottleneck is almost never the network

This is the part nobody says, and it is the reason most 10GbE upgrades disappoint.

Run the arithmetic against your own storage before you spend anything:

A single hard drive gives you under a quarter of the link. A SATA SSD cannot reach half of it, and that is the interface ceiling before the flash behind it has any say. Four drives reading perfectly sequentially finally approach the wire, and nothing reads perfectly sequentially — the six-bay rebuild math covers what happens to those numbers once parity and scattered blocks are in play.

Saturating 10GbE takes NVMe or a genuinely fast array. Most people adding 10GbE do not have one.

And then there is SMB

Even with the storage to feed it, a single file copy will sit well under the link, and the protocol is why. Microsoft’s own account of the problem: with one SMB session and no Multichannel, SMB opens a single TCP connection, and that connection gets affinitized to a single CPU core. One copy, one connection, one core. A faster switch does not sell you a second core.

SMB Multichannel is the fix. On an RSS-capable NIC it opens several TCP connections for the same session and spreads them across cores. It is on by default on Windows. On TrueNAS SCALE it is a toggle under Advanced Settings in the SMB service, and flipping it costs nothing.

Check both of those before you buy hardware. “Just add 10GbE” is the most common wrong assumption in home networking, and the two things it usually fails to fix are sitting in your NAS and in your file-sharing config.

ConnectX-3 is done

The used ConnectX-3 was the budget answer for years and it is now the wrong buy at any price.

VMware’s list of devices dropped in ESXi 8.0 covers everything the nmlx4_en driver ever served, and Broadcom’s own wording is blunt: “The driver does not exist in ESXi 8.0.” Not deprecated, not degraded — absent. NVIDIA reached the same place in its own stack earlier: ConnectX-3 and ConnectX-3 Pro stopped being supported as of MLNX_OFED 5.1, with anyone who still needs the card pointed at the 4.9 long-term-support branch. NVIDIA’s current ESXi driver line begins at ConnectX-4.

One window is still open, and it is worth knowing which one. The mlx4 module remains in the mainline Linux kernel, so a card already in a Proxmox or TrueNAS box will keep coming up. Leave a working one alone. Do not buy another. My earlier budget 10GbE build put its cheapest tier on these cards, and on a Linux host that tier still runs — on ESXi 8 it does not, and I would start any new build on something newer either way.

Used enterprise NICs are still the right buy

None of the above is an argument against used enterprise silicon. It is still excellent value, and the risk was never that the hardware dies. The risk is driver and firmware support, which is exactly what ended ConnectX-3.

So invert the shopping order. Check what your hypervisor’s current release ships a driver for, then look at prices. On ESXi that puts your floor at ConnectX-4. On Linux the window is wider, but “the kernel still builds the module” is a different thing from “someone is developing it,” and the gap between those two closes in one direction only.

What to buy

Most people reading this should not buy 10GbE. Buy storage.

If your NAS is one or two spinning disks, the cable is not what is slowing you down and a switch will not change your transfer rate by a meaningful amount. The same money in an NVMe drive, or in enough spindles to read in parallel, moves the number the network cannot. Turn on SMB Multichannel while you are at it — it is free and it is the second most common cause.

If your pool already clears a gigabyte a second, the shopping order is short:

1. A fanless SFP+ switch. The CRS305 for four ports, the CRS309 for eight. If you buy a fanned switch anyway, budget for the replacement fan on the same order.
2. Passive DAC for anything under five meters. Fiber past that, and only past that.
3. ConnectX-4 or newer. Used, secondhand, from whoever is cheapest — but check the driver first and the price second.

The 2.5GbE comparison is the other answer here. For a NAS on one or two spinning disks, 2.5GbE is already faster than the drives, and it costs a fraction of this. That is not a consolation prize; for most homes it is the correct stopping point.

Wrong for

Wrong if you want silence without a fan swap. Buy passive-cooled or plan the replacement into the purchase — do not buy a fanned switch and hope.

Wrong if you expect 10GbE to fix a storage problem. It will move your bottleneck from a place you can see to a place you cannot, and your copies will finish at the same time.

Wrong if the card is too old for your hypervisor. The price on a dead-driver NIC is not a bargain, it is the market telling you something.