10 Proxmox Mistakes You Don't Want to Make (and What to Do Instead)

If you've ever gone down the rabbit hole of home labs, you've probably heard of Proxmox — the beloved open-source virtualization platform. It's powerful, flexible, and completely free. But that freedom also comes with a learning curve that bites back if you're not careful. One user decided to save others from that pain and dropped a mini-manual of hard-earned lessons from their own experience. Their open PDF guide outlines 10 common Proxmox mistakes, and the community response? A mix of "thank you" and "same here." Turns out, these aren't just rookie blunders — even seasoned users have face-palmed their way through some of these. Here's a deeper look at those 10 Proxmox pitfalls, plus commentary and context from the broader Proxmox community. ## 1. ZFS Without Proper RAM Planning ZFS is incredible… until it eats your system alive. The old rule of thumb is one gigabyte of RAM per terabyte of raw storage. Ignore that, and ZFS can tank your performance — or worse, crash your system entirely. One user noted confusion around this rule, pointing out inconsistencies in the author's own math. But the takeaway remains: if you're using ZFS, you need to be intentional with your memory allocation. And if your system has under 16GB of RAM, maybe ZFS isn't the best choice. **What to do instead:** Calculate your storage-to-RAM ratio and consider whether adding L2ARC or SLOG makes more sense than throwing in more memory. ## 2. The "ECC is Mandatory" Myth Ah, the eternal ECC debate. Some claim ZFS without ECC RAM is asking for data corruption. Others call that fearmongering. One contributor laid it out best: ECC doesn't stop bitflips — it logs and corrects them. Without ECC, you might experience silent corruption. But it's not a guarantee. It comes down to how much you value your data — and how bulletproof you want your system. **What to do instead:** If your data really matters, invest in ECC. If you're experimenting, backups and smart design matter more than obsessing over memory type. ## 3. Using RAIDZ for VM Storage RAIDZ is built for big, sequential files — think media libraries or backups. VMs? Not so much. Because RAIDZ writes stripes across multiple disks, random I/O becomes a bottleneck. Proxmox veterans say this is a common early mistake. For VM-heavy setups, striped mirrors (ZFS mirrors) offer far better performance and resilience. **What to do instead:** Use mirrors or even ZFS striped mirrors (RAID10-like setup) for your VMs. Save RAIDZ for cold storage. ## 4. Dismissing Local-LVM as Inflexible Many users assume Local-LVM is too rigid to be useful. But it's often the fastest storage method out of the box, and for small deployments, it works just fine. Yes, it lacks snapshots and advanced features that ZFS offers, but it's stable and simple. **What to do instead:** Start with Local-LVM if you don't need bells and whistles. You can always migrate later as your needs grow. ## 5. The "Host" CPU Type Trap On paper, using the host's exact CPU features for your VM sounds great — max performance, right? But here's the gotcha: you won't be able to migrate that VM to another machine if the CPU isn't identical. One user mentioned even greater issues: when using "host" CPU, mitigations for Spectre and Meltdown might be missing unless manually handled. **What to do instead:** Choose a generic CPU model like x86-64-v2-AES to balance performance and compatibility. Use "host" only if you're absolutely sure the VM won't need to migrate. ## 6. Setting Up HA Without Meeting Requirements Proxmox HA (High Availability) isn't plug-and-play. A lot of users set it up with two nodes and no quorum device — which is a recipe for split-brain situations. You need three votes for quorum. That usually means three physical nodes, or two nodes plus a QDevice. Skimp here, and you'll end up with VMs stuck in limbo — or worse, dual nodes trying to run the same VM. **What to do instead:** Use three nodes or two nodes plus a QDevice. And make sure fencing is properly configured. ## 7. Incomplete Backup Strategy Backups aren't just "nice to have" — they're non-negotiable. One misstep, and your entire VM could vanish. The guide emphasizes planning not just where and when you back up, but also how you restore. One user chimed in with a crucial addition: always test your backups. A backup that fails to restore is a paperweight. **What to do instead:** Automate daily or weekly backups, store them remotely (or at least off-disk), and do test restores every now and then. ## 8. Running Docker Directly on Proxmox This one triggered a chorus of "why would anyone…" — and yet, it's surprisingly common. Running Docker on the Proxmox host mixes containers and hypervisors, which is a stability and security nightmare. The recommendation is simple: isolate. Either run Docker in an LXC container or spin up a lightweight VM just for container management (hello, Portainer or Rancher fans). **What to do instead:** Don't run Docker on the bare Proxmox node. Use a VM or LXC, and keep your hypervisor clean. ## 9. No Monitoring Until It Breaks This is the "silent killer." Most users skip monitoring until something explodes — and by then, logs might be useless. The original guide touches on basic monitoring, but some community members argue for more advanced setups: SNMP traps, email alerts, Prometheus + Grafana, or at least an agent-based solution. **What to do instead:** Set up monitoring on day one. Even basic email alerts are better than nothing. ## 10. Deploying Services Directly on the Hypervisor You wouldn't install your apps on the car's engine block, so why would you deploy services on your hypervisor? Proxmox is not a general-purpose Linux distro. It's meant to be lean and focused. Adding services increases your attack surface and makes updates more dangerous. **What to do instead:** Put your services in VMs or containers. Leave the hypervisor alone. ## Honorable Mentions from the Community - Cloning Windows VMs without Sysprep. - Deleting LXC storage pools that are still referenced. - Not using time synchronization — especially critical for TOTP authentication. - Trusting external power supplies on Minisforum servers (replace them early!). ## Final Thoughts Proxmox is like a blank canvas — you can build something amazing, or you can paint yourself into a corner. The trick isn't avoiding mistakes altogether — it's learning the right lessons quickly. And thanks to one user's transparency (and a passionate community's deep dive), you don't have to learn everything the hard way. So before your next `qm create` or `zfs pool create`, take a beat. Reread this. Save yourself the drama. Because the only thing worse than a corrupted VM is realizing you caused it yourself.