SCS vs. Proxmox + K3s: Choosing a Base for openDesk Edu
The base platform decision comes before the service decision. openDesk Edu is Kubernetes-native — its services ship as Helm charts, GitOps manifests, and container images — so the practical question for an institution is not which applications to run, but how to obtain a Kubernetes platform that a small team can operate sustainably. This article compares two widely used approaches in German higher education: the Sovereign Cloud Stack (SCS) standard and a self-operated stack of Proxmox VE with K3s. It describes both factually and outlines the factors that typically decide between them.
Two Approaches to the Same Requirement
SCS: A Standard, Not a Product
The Sovereign Cloud Stack (SCS) is a standard for sovereign cloud infrastructure, developed by a community under the auspices of the Open Source Business Alliance (OSBA). It defines interoperable layers for infrastructure-as-a-service (OpenStack-based) and container platforms (Kubernetes), along with reference implementations that providers and operators can adopt.
SCS is significant because it operates at the level of certification. Operators can achieve SCS-compatible or SCS-sovereign status, which signals that their cloud offers standardized, portable interfaces. For public-sector institutions, this certification is relevant to procurement: it provides a documented basis for comparing providers, and it aligns with compliance frameworks such as the German government's container requirements.
The key property of SCS is portability through standardization — a workload that runs on one SCS-certified platform should run on any other, and the interfaces are specified openly rather than by a single vendor.
Proxmox VE + K3s: A Self-Operated Stack
Proxmox VE is an open-source virtualization platform (KVM and LXC based) maintained by Proxmox Server Solutions GmbH, with a large community in European higher education. K3s is a lightweight, CNCF-certified Kubernetes distribution maintained by SUSE/Rancher, designed for resource-constrained and edge deployments.
Combined, they form a pragmatic, fully self-operated platform: Proxmox VE provides virtualization and storage management, K3s provides the Kubernetes control plane on top. This combination is popular in universities because it is operable by a small team, well documented, and free of subscription obligations in its basic form.
The key property of this approach is operational simplicity — two well-understood open-source components, no certification process, and complete control over every layer.
Comparison
| Dimension | SCS | Proxmox VE + K3s |
|---|---|---|
| What it is | A standard with reference implementations | A concrete virtualization and container stack |
| Governance | Community-driven under OSBA, public funding context | Vendor-maintained (open source), community ecosystem |
| Certification | SCS-compatible / SCS-sovereign levels | None |
| Portability | Standardized interfaces between certified platforms | Specific to the chosen components |
| Operations | Requires understanding of the full SCS reference stack | Two components, well-documented, small-team friendly |
| Procurement fit | Directly usable in sovereign cloud procurement | Indirect — evaluated on technical merits |
| Sovereignty alignment | Explicit goal of the standard | Achieved through self-operation of open source |
| Typical operator | Cloud providers, larger institutions, consortia | Single institutions, small IT teams |
Neither approach is inherently better; they address different institutional contexts.
Decision Factors
Team Size and Skills
SCS presumes the capacity to operate a full cloud stack — even with reference implementations, the operational surface is large. Proxmox VE + K3s fits institutions where two or three people run the entire platform. If the team can already operate OpenStack or a certified SCS platform, SCS is the lower marginal cost; if the team's strength is virtualization and Linux administration, the Proxmox + K3s route is more direct.
Procurement and Compliance Context
For institutions that must demonstrate interoperability or participate in sovereign cloud procurement frameworks, SCS certification is a documented, auditable asset. For institutions procuring hardware and software directly, the self-operated stack can be specified on technical merits alone.
Portability Needs
If workloads must be movable between providers — for example, as part of a consortium or a cloud strategy with several providers — SCS's standardized interfaces reduce the cost of that movement. If workloads stay on institutional hardware for their lifetime, portability between providers is rarely exercised, and the simpler stack suffices.
What openDesk Edu Requires from Either Base
Regardless of the choice, openDesk Edu imposes the same base requirements:
- Kubernetes 1.28 or later, with a working ingress controller and persistent storage classes
- Identity federation via SAML or OIDC (openDesk Edu ships Keycloak, which can federate with DFN-AAI / eduGAIN)
- GitOps tooling (ArgoCD) or Helm/Helmfile-based deployment
- Monitoring and logging (the platform includes Prometheus, Grafana, and Loki)
- Container images from a registry the cluster can reach
Both SCS-certified platforms and K3s clusters satisfy these requirements. SCS adds standardized storage and networking interfaces; Proxmox + K3s provides them through the chosen components directly.
Practical Observations
- Start with the smallest platform you can sustain. Kubernetes itself is identical on both bases; the differences are in the surrounding infrastructure.
- Storage is the decisive operational factor. Both approaches need reliable persistent storage classes; Proxmox VE's native storage management and SCS's standardized storage interfaces both work, but the operations model differs.
- Upgrades differ in scope. K3s upgrades are small and frequent; SCS reference stack upgrades touch more components. Institutions with limited upgrade windows should account for this.
- Neither approach locks you out of the other. A Proxmox + K3s deployment can later be migrated to an SCS-certified platform using standard Kubernetes tooling, since the workload manifests are portable by design.
Summary
| Consideration | Points toward |
|---|---|
| Small team, self-operated, direct control | Proxmox VE + K3s |
| Procurement certification, provider portability | SCS |
| Existing OpenStack / SCS skills | SCS |
| Existing virtualization / Linux skills | Proxmox VE + K3s |
| Workloads stay on institutional hardware | Proxmox VE + K3s |
| Consortium or multi-provider cloud strategy | SCS |
openDesk Edu runs on Kubernetes; it does not prescribe the base. The choice between SCS and Proxmox + K3s is a choice about governance, portability, and the operational capacity of the institution — not about the applications themselves.
Get Started
- Review the requirements: The deployment guide describes what any base platform must provide.
- Evaluate both bases: Use the decision factors above against your institution's team, procurement, and portability context.
- Join the discussion: The openDesk Edu community welcomes reports from institutions running either base. Share your experience in the community of practice.
openDesk Edu is the education variant of openDesk, extended with a comprehensive suite of services for research and teaching. Source code is available on GitHub and opencode.de.
