Turn an Old Gaming PC Into a Proxmox Home Server: Costs, ZFS, GPU and Backup Risks

The "free" part of the headline needs some qualification, and so does the idea that any old PC can do the same job. The build itself is a good example of how a retired gaming rig can become a useful home lab, and of where the hidden costs and risks are.

The build in brief​

According to Sherback, the server is a mix of parts he already had and a few targeted purchases:

The services he runs are Immich (a self-hosted alternative to Google Photos), Jellyfin for media streaming, Samba file shares, a Minecraft server, a Counter-Strike 1.6 server, TeamSpeak for voice chat, and NetBird for remote access without forwarding ports on his router.

Bottom line: the CPU platform, SSD and GPU cost nothing extra. Storage, networking and the case did. The software was free; the build as a whole wasn't.

What "free" actually means with Proxmox​

Proxmox VE is a hypervisor that combines KVM virtual machines with LXC containers, and you manage it through a web interface. Proxmox says on its developer page that its code is entirely open source, mostly under AGPLv3 or a similar free licence. Paying for a subscription gets you two things: access to the Enterprise repository and technical support. Neither one unlocks extra features.

There's a catch that trips up a lot of first-time installers. If you install Proxmox VE and run apt update, you'll probably get an error about a missing subscription key, because Proxmox ships with the Enterprise repository enabled by default and that repository requires a paid licence.

The fix is official and documented. Proxmox's Package Repositories wiki describes the pve-no-subscription repository and says you don't need a subscription key to access it. It's meant for testing and non-production use, and Proxmox doesn't recommend it for production servers because its packages aren't always as heavily tested and validated.

For a home lab, that's usually a reasonable trade. Here is the procedure for Proxmox VE 9 (based on Debian "trixie"), following Proxmox's own documentation:

1. Turn off the Enterprise repository. Add an Enabled: no line to the relevant entry in the repository file. This stops the error messages on hosts without a subscription key.
2. Add the no-subscription repository. Proxmox recommends configuring it in /etc/apt/sources.list.d/proxmox.sources, with these entries:
   
   Code:

   Types: deb
   URIs: [Index of /debian/pve/](http://download.proxmox.com/debian/pve)
   Suites: trixie
   Components: pve-no-subscription
   Signed-By: /usr/share/keyrings/proxmox-archive-keyring.gpg

3. Keep the Debian repositories. Proxmox notes that you will always need the base Debian repositories in addition to a Proxmox VE repository.
4. Check that it worked. Run apt update. If it finishes without 401 or subscription errors, you're set.

Ceph has its own repositories. Proxmox describes the Ceph no-subscription repository as suitable for testing and non-production use, freely accessible without a valid subscription, with its package versions later made available in the enterprise repository. Most single-node home labs never touch Ceph, but if your install includes the ceph.sources file pointing at the enterprise server, it will throw the same errors.

Older Proxmox 7 and 8 guides use the one-line .list format, and on version 9 those instructions will leave you with a mix of formats. Make sure the guide you follow matches your version.

Is a ten-year-old CPU really enough?​

On paper, the 6700K meets the requirements. Intel's spec sheet lists 4 cores and 8 threads, a 4.00GHz base clock, a 4.20GHz maximum turbo, a 91W TDP, and support for VT-x, VT-d, Extended Page Tables and Quick Sync Video. Proxmox's hardware requirements ask for an Intel VT or AMD-V capable CPU for KVM virtualization, plus VT-d or AMD-Vi for PCIe passthrough. The chip passes both.

Intel's spec page also shows a few things the original piece doesn't mention:

• No ECC memory support. Plenty of ZFS home labs run on non-ECC RAM without trouble, but you should know you're giving up that protection.
• Maximum of 64GB RAM. 32GB leaves room to grow, but there's a hard limit.
• End of servicing. Intel lists the chip as discontinued, with servicing updates ending September 30, 2022. For a box that runs all the time and is reachable remotely, that matters more than it does for a retired gaming PC.
• 16 PCIe 3.0 lanes from the CPU, which can be split as 1×16, 2×8 or 1×8+2×4. With a GPU, an HBA and a NIC all installed, how the lanes get shared depends on your motherboard. Check the manual before you assume every card gets full bandwidth.

On memory, Proxmox recommends at least 2GB for the host and its services, plus whatever your guests need. ZFS needs more, roughly 1GB per TB of storage used. A two-drive 8TB mirror holds about 8TB of usable data (not 16TB), so that guideline fits easily in 32GB.

Bottom line: most older Intel and AMD desktop chips have the virtualization extensions, but turn them on in the firmware first and look at the platform's limits before you plan a big setup.

Containers vs. VMs​

Sherback runs most of his services in LXC containers instead of full virtual machines, and that's sensible on older hardware. Proxmox's documentation explains that containers share the host's kernel instead of emulating a whole operating system, so they have less overhead. The downside is that they can only run Linux guests.

Proxmox's own docs also say that if you want application containers such as Docker images, it's best to run them inside a QEMU VM. You keep the benefits of containers and get the stronger isolation a VM provides. This matters for Immich in particular: the Immich documentation says its hardware-acceleration instructions are written for Docker Compose and that other container engines may need different configuration. Sherback doesn't say exactly how he deployed Immich, so anyone copying the build will have to choose between Docker inside a VM and other approaches themselves.

Also, separate containers keep services tidy, but don't treat them as the same as separate physical machines for security.

Storage: the part that deserves your money​

Sherback says storage was the first thing he spent money on, and that was the right call. Proxmox's requirements say plainly that neither ZFS nor Ceph is compatible with a hardware RAID controller. That's why he used an HBA flashed to IT mode, which passes each disk directly to the operating system.

He also hit a well-known quirk. Cards like the LSI 9207-8i can conflict with some Intel consumer motherboards over two SMBus pins on the card's connector, and covering those pins with tape fixed it on his Z170 board. That's a fix reported by one builder, not something the manufacturer endorses, so try it at your own risk.

The two used Exos drives run as a ZFS mirror. OpenZFS documentation defines a mirror as a vdev that stores the same data on two or more drives. A two-disk mirror can survive one drive failing. It is not a backup:

• If you delete a file or ransomware encrypts it, the change is written to both disks immediately.
• Used enterprise drives can come from the same batch with similar wear, so a second failure while the mirror is rebuilding is possible.
• Run zpool status regularly. OpenZFS documents it as the command that shows the health and layout of every vdev.

If your family photos live in Immich, keep a separate copy somewhere else.

The 2.5GbE card has a practical reason behind it. Sherback says a single modern hard drive can read large files faster than gigabit Ethernet can carry them, so the network would otherwise be the bottleneck.

The RTX 3080 does a second job​

Sherback says the reused GPU is a big reason the server performs better than its age suggests:

• Immich uses CUDA for face recognition and smart search. Immich's documentation confirms both can run on the GPU, but calls the feature experimental. CUDA needs a GPU with compute capability 5.2 or higher, an official Nvidia driver version 545 or newer, and, on Linux, the Nvidia Container Toolkit.
• Jellyfin uses NVENC for transcoding. Jellyfin's documentation says hardware acceleration works on Nvidia GPUs from Maxwell onward, works on headless servers, and in Jellyfin 10.11 needs Linux driver 520.56.06 or newer. It also notes that some low-end and mobile models don't have NVENC/NVDEC at all.

If you don't have a spare graphics card, Sherback points out that the 6700K's built-in Quick Sync encoder is quite capable, though a modern discrete GPU will do better.

The bigger picture​

The broader point holds up: a retired PC with a modern hypervisor is one of the cheapest ways to learn virtualization, ZFS and self-hosting, all skills that carry over to work in enterprise IT. Windows users can run the same idea on Hyper-V, but Proxmox's web interface and built-in container support are why so many home labs use it.

Some caveats are missing from the original account. It gives no figures for power draw, noise, temperatures or uptime, and it doesn't describe a backup plan. A 91W-TDP desktop running around the clock will add something to the electricity bill. Sherback's NetBird setup also wasn't independently checked; avoiding port forwarding is a good idea, but you still need to configure access controls carefully.

The takeaway: install Proxmox, switch to the no-subscription repository, start with one container, and spend your first upgrade budget on storage you trust and a backup you've actually tested. A dusty gaming PC can do a lot more than sit in a closet, as long as you know its limits.