From ESXi to Proxmox: what a migration really costs

Since Broadcom switched VMware licenses, we regularly get the same question: "What's the real cost of switching to Proxmox?" The honest answer: less than many fear, but more than zero. In this article, we calculate the cost blocks of a typical migration the way we actually perform them for small and medium-sized enterprises.

Why switch at all?

The trigger is almost always the same: the VMware bill. After the Broadcom acquisition, perpetual licenses were abolished, small packages discontinued, and prices in some cases multiplied. Anyone who previously used free ESXi or an Essentials license suddenly faces subscription costs that are simply disproportionate for an operation with two or three servers.

Proxmox VE is a mature alternative: open source, established for over 15 years, with optional vendor support from Vienna. The virtualization itself (KVM) is the same technology that major cloud providers build on. For typical SME deployments with Windows servers, domain controllers, file servers, and a few business applications, Proxmox lacks nothing relevant.

How a migration actually works

Our approach is always structured the same way because it has proven effective:

1. Inventory assessment. Which virtual machines are running, how large are they, what dependencies exist? This sounds trivial, but surprises regularly emerge here: forgotten test VMs, an old application nobody knows anymore, or a backup that has been failing for months without anyone noticing.

2. Build the target environment. Either on new hardware (the cleanest approach) or on a cleared existing server. Proxmox is installed, network and storage configured, and crucially: backup first. We use Proxmox Backup Server (PBS) for this, which creates incremental, deduplicated backups and allows restoration of individual files. Migration only begins once backup is proven to work.

3. Per-VM migration. Virtual disks are exported from ESXi and imported into Proxmox. For Windows VMs, VirtIO drivers are then added so network and disk run at full speed. We plan a maintenance window per VM, usually an evening is sufficient. Critical systems like the domain controller come last, once the process is well-established.

4. Parallel operation. The old ESXi remains powered off for a few weeks but ready to start. This is the insurance: if an application does encounter problems, the old VM can be brought back online on short notice. In practice we rarely needed it, but it reassures everyone involved.

5. Post-migration work. Set up monitoring, fine-tune backup schedules, update documentation, properly decommission old hardware.

The honest cost blocks

Now for the numbers. A migration consists of four blocks:

Analysis and planning: depending on environment size, half to a full working day. This is where you decide what gets migrated, in what order, and with which maintenance windows.

Per-VM migration: the largest block. A straightforward Windows VM is relocated in one to two hours, including drivers and functional testing. A VM with large data disks or a sensitive business application can take half a day. With ten VMs you realistically end up at two to four working days.

Parallel operation: costs mainly electricity and some attention, but hardly any working time. You should budget for it anyway, as it prevents costly emergency actions.

Post-migration work: one to two days for backup verification, monitoring, and documentation. This block is most often skipped and almost always comes back to haunt you.

Against this stands the savings: no more VMware subscription costs. An optional Proxmox support subscription costs a fraction of what Broadcom charges today for comparable environments. For most of our customers, the migration has paid for itself within one to two years through license savings alone.

What is often underestimated

Three points that should not be missing from any quote: First, the backup concept. Anyone coming from Veeam needs to know that the familiar solution has only recently started working with Proxmox; PBS is the native and in our view better choice. Second, VirtIO drivers for Windows: without them the VM runs but noticeably slower. Third, knowledge in-house: the interface is different, but the concepts are largely similar. A brief orientation for the person who handles internal first contact for IT questions is always part of our approach.

Conclusion

An ESXi-to-Proxmox migration is not rocket science, but also not an afternoon project. If you work with realistic planning, a functioning backup, and orderly parallel operation, you get a virtualization platform without license pressure that is technically on par. The license shock from Broadcom was annoying for many businesses; in hindsight for most it was the impetus to a better and more cost-effective solution.

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