# A mini PC or old laptop as a Proxmox host: sizing the box

> How many Windows VMs a small host can carry, what cores and RAM to buy, and the NIC and storage choices that decide whether it is usable.

**Tested on**

- Build: 26300.9457 / 26100.33650
- Edition: Pro (26H2) / Server
- Architecture: x64
- Evidence: E1
- Verified: 2026-10-29

## The short answer

A homelab host is sized by **RAM first, cores second, storage third, network fourth**. Everything else is a detail.

Rules that hold up:

- **RAM is the hard limit.** A Windows 11 VM wants 6–8GB to be pleasant; Server Core can run in 2–4GB.
- **Two vCPUs per VM** is enough for most lab work; oversubscribing vCPUs raises latency.
- **SSD/NVMe only.** Thin-provisioned Windows VMs on spinning disks are painful.
- **One NIC is fine** to start; a second one makes a lab much more interesting later.

## The sizing table

| Host | Comfortable Windows guests |
|---|---|
| 16GB RAM, 4 cores | 1 (8GB) + a container or two |
| 32GB RAM, 8 cores | 3 (8GB each), or 2 + Server Core |
| 64GB RAM, 12–16 cores | 6–7 mixed guests |
| 96GB+ | a rack in a box |

This site's lab is a **16-core / 31.2GB** Proxmox host running two 8GB Windows 11 VMs. That fits, but with little room: a third 8GB guest needs memory freed first.

## What actually matters when buying

| Spec | Why it matters |
|---|---|
| RAM (soldered on most mini PCs) | the limit you cannot upgrade |
| NIC | **Intel i225/i226 or better**; Realtek 8125 works but has quirks |
| Storage | NVMe slot count, and whether the box takes a 2.5" drive |
| CPU TDP / cooling | a 15W part is quiet but slow with 3 VMs |
| Idle power | a homelab runs 24/7; 10W vs 30W matters on the bill |
| vPro/AMT or IPMI | remote console without a monitor |

Mini PCs usually have **soldered RAM and one NVMe slot**. Buy the RAM capacity you will want in a year, not the one you need today.

## Old laptop vs mini PC

| | Old laptop | Mini PC |
|---|---|---|
| Cost | free if you have it | cheap |
| RAM | often upgradeable (SO-DIMM) | usually soldered |
| Storage | one SATA + maybe M.2 | one or two M.2 |
| Network | 1 GbE + Wi-Fi | 2.5GbE typical |
| Reliability | battery as a UPS (a plus) | needs its own UPS |
| Lid/thermal | clamshell cooling, dust | better airflow |

An old laptop is an excellent first host precisely because it is free and has a built-in UPS. Its weakness is one disk and one NIC.

## Proxmox setup that avoids pain

1. Install PVE with **ZFS on a single disk** (or ext4/lvm-thin if RAM is tight — ZFS wants RAM).
2. Create a **Windows VM** with `q35`, OVMF, vTPM 2.0, VirtIO SCSI, VirtIO NIC.
3. Install **VirtIO drivers** during setup, or the disk list is empty.
4. Use **`--cpu host`** if you want nested virtualisation (WSL2/Hyper-V inside the guest).
5. Keep a **template** and clone; do not reinstall Windows per experiment.

```text
Guest sizing that works on a 32GB host:
  Windows 11 Pro  8GB / 4 vCPU / 64GB disk
  Windows Server  4GB / 2 vCPU / 40GB disk
  Linux service   2GB / 2 vCPU / 16GB disk
```

> **Caution: Do not enable ballooning and then wonder why the guest is slow**
>
> Memory ballooning lets the host reclaim RAM from a guest under pressure. It is a safety valve, not a sizing strategy: a guest that is routinely squeezed performs badly and may fail to start applications. Size the guests to fit, and use ballooning only as headroom.

## Power and noise

- A 15W mini PC is effectively silent; a 35–45W part with a small fan is audible in a quiet room.
- Put the host where you will not hear it, and give it airflow.
- A cheap UPS (even a small one) prevents the corruption that an unclean shutdown causes on any guest filesystem.

## Related

- [PVE host memory planning](https://winbook.fyi/en/hardware/homelab/host-memory/)
- [Windows VM on Proxmox](https://winbook.fyi/en/windows/dev/pve-windows-vm/)
- [Used server hardware](https://winbook.fyi/en/hardware/homelab/used-server/)

## Lab boundary

E1 for the sizing guidance (Proxmox and Microsoft documentation). The host figures quoted are this site's lab record, not a benchmark; see the host-memory page for how they were observed.

## Sources

- [Proxmox VE — Windows 11 guest best practices](https://pve.proxmox.com/wiki/Windows_11_guest_best_practices)
- [Proxmox VE — Storage](https://pve.proxmox.com/wiki/Storage)
- [Microsoft Learn — Windows Server hardware requirements](https://learn.microsoft.com/en-us/windows-server/get-started/hardware-requirements)

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Source: https://winbook.fyi/en/hardware/homelab/mini-pc-host/