Question 1

Why consider KVM now?

Accepted Answer

The virtualization market shift — including new licensing and packaging models following Broadcom's acquisition of VMware in November 2023 — is turning renewals into architecture decisions. KVM has been in the mainline Linux kernel since 2007 and is supported by SUSE on SLES.

Question 2

Is VirtStack another hypervisor or "just a KVM GUI"?

Accepted Answer

Neither. It is a Day-2 control plane that sits above SLES, KVM, libvirt and Pacemaker and replaces none of them. It adds preflight checks, placement policy, HA safeguards and an audit trail — not just buttons for virsh.

Question 3

What is VirtStack?

Accepted Answer

An enterprise management platform for KVM hypervisors on SUSE Linux Enterprise Server. It provides a web console for host onboarding, VM lifecycle, virtual hardware, storage, networking, snapshots and clones, NUMA-aware placement, live metrics and HA cluster visibility.

Question 4

How is it different from Proxmox VE or oVirt?

Accepted Answer

VirtStack does not replace your hypervisor OS. It manages SUSE-supported KVM hosts, so your hypervisors stay on an enterprise-supported distribution with SUSE's lifecycle and certifications. Its outbound-agent model also means no central SSH keys and no inbound ports on hosts.

Question 5

How does it compare with Nutanix or other HCI?

Accepted Answer

HCI integrates hypervisor, storage and management into one platform. VirtStack runs on your SLES hosts and your existing SAN or NAS, with no new storage platform. (Nutanix AHV is also KVM-based; the difference is the operating model, not the hypervisor.)

Question 6

Is VirtStack a vSphere replacement?

Accepted Answer

For many vSphere environments, yes — lifecycle, console, templates/clones, placement and HA visibility are covered today. Live migration and DRS-style automated rebalancing are on the roadmap, so review the roadmap against your requirements.

Question 7

Which SLES versions are supported?

Accepted Answer

SLES 15 SP6 and SP7 on x86_64. See system requirements in the documentation.

Question 8

Do I need SUSE subscriptions?

Accepted Answer

Yes. Each hypervisor needs a SLES subscription, plus SUSE Linux Enterprise High Availability if you run Pacemaker clusters. VirtStack is licensed separately.

Question 9

Can VirtStack manage VMs that already exist?

Accepted Answer

Yes. Existing libvirt domains are discovered on enrollment, and you can open their consoles immediately.

Question 10

Which guest operating systems work?

Accepted Answer

Any guest supported by KVM/QEMU on SLES, including SLES, RHEL-family, Ubuntu, Debian and Windows Server / Windows 11 (with vTPM). Install VirtIO drivers on Windows guests for best performance.

Question 11

Does it support GPU passthrough?

Accepted Answer

Yes, via VFIO PCI passthrough, provided IOMMU is enabled and the device is in an isolated IOMMU group.

Question 12

What storage can I use?

Accepted Answer

Local directory pools, NFS and LVM today. Software-defined shared storage orchestration is on the roadmap.

Question 13

Can I migrate VMs between hosts?

Accepted Answer

The migration wizard validates capacity and compatibility across hosts today. Live zero-downtime migration and storage migration without shared storage are on the roadmap.

Question 14

Is it suitable for SAP HANA?

Accepted Answer

SAP HANA can run on KVM in configurations that follow SUSE's SAP HANA on KVM best-practice guide (SLES for SAP applications 15 SP7) and SAP Note 2284516; check CPU generation and scenario in SAP Note 2235581 and the SAP HANA Hardware Directory. VirtStack exposes the relevant controls (NUMA pinning, strict memory policy, host-passthrough); a dedicated HANA workload profile is planned. VirtStack itself is not SAP-certified.

Question 15

How does HANA System Replication relate to VM HA?

Accepted Answer

They are different layers. HSR, automated by SUSE's SAPHanaSR agents in a guest cluster, protects the database with a hot standby. Host Pacemaker restarts general-purpose VMs on a surviving node after fencing.

Question 16

How do we migrate VMware VMs?

Accepted Answer

Convert copies with virt-v2v (shipped with SLES), validate, then operate them in VirtStack. Keep source VMs intact until sign-off so rollback is just powering them back on.

Question 17

Does the control plane store root passwords or SSH keys?

Accepted Answer

No. Agents authenticate with per-host certificates over mutual TLS.

Question 18

What ports do I need to open?

Accepted Answer

Outbound TCP 443 from hypervisors to the control plane, and inbound TCP 443 to the control plane from administrators. Nothing inbound on hypervisors.

Question 19

Are VM consoles exposed on the network?

Accepted Answer

No. Display servers listen on 127.0.0.1 only; console traffic is relayed through the agent tunnel.

Question 20

Is there RBAC and SSO?

Accepted Answer

RBAC, OIDC/SAML SSO and MFA are on the roadmap (Phase 11). Today, restrict access to the control plane via network controls.

Question 21

Can it run air-gapped?

Accepted Answer

Yes. Offline, signed installation bundles are available.

Question 22

What happens if the control plane goes down?

Accepted Answer

Running VMs are unaffected. Hosts continue as normal libvirt hypervisors, and agents reconnect automatically when the control plane returns.

Question 23

How do we handle host maintenance?

Accepted Answer

Maintenance mode cordons the host so no new VMs land on it; existing VMs are moved with the migration wizard. One-click evacuation is on the roadmap.

Question 24

Does VirtStack build our Pacemaker cluster?

Accepted Answer

No. Cluster build is Day 0 work with SUSE HA tooling such as crmsh. VirtStack discovers and visualises it, and fencing and failover are always performed by Pacemaker.

Question 25

Will changes made with virsh confuse VirtStack?

Accepted Answer

No. It reads live libvirt state and receives lifecycle events in real time, so VMs created or changed outside it are visible.

Question 26

Is there an API or Terraform/Ansible support?

Accepted Answer

A public API and Terraform/Ansible integration are under evaluation, not yet committed.

Question 27

What happens if a host loses network connectivity?

Accepted Answer

Its VMs keep running. The agent reconnects with exponential backoff and resynchronises state.

Question 28

Does VirtStack interfere with Pacemaker?

Accepted Answer

No. It reads cluster state and performs relocations through Pacemaker. Actions on cluster-managed VMs are blocked if quorum is lost.

Question 29

How many hosts can one control plane manage?

Accepted Answer

Current releases use a single gateway; horizontally scaled gateways for 50+ hypervisors are on the roadmap.

Question 30

Can I export metrics to Prometheus/Grafana?

Accepted Answer

Not yet — this integration and long-term metric history are on the roadmap.

Question 31

Can I uninstall VirtStack cleanly?

Accepted Answer

Yes. Remove the agent package; your VMs remain standard libvirt domains.

Question 32

Is open source free?

Accepted Answer

No. SUSE subscriptions, VirtStack licensing, skills and migration effort all apply. We build a customer-specific TCO model rather than quoting savings percentages.

Question 33

Who supports what?

Accepted Answer

SUSE supports SLES, KVM and SUSE HA; VirtStack is supported by its vendor under your subscription.

Question 34

How is VirtStack licensed?

Accepted Answer

Per physical CPU socket on managed hypervisors, billed annually.

Question 35

Is there a free trial?

Accepted Answer

Yes — a 60-day evaluation for up to 4 sockets.

Question 36

Do roadmap features cost extra?

Accepted Answer

No. Eligible tiers receive them as they reach general availability during the subscription term.

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