RWX (ReadWriteMany) volumes in Cozystack — native shared storage for your workloads
Starting with Cozystack v1.0, you can use ReadWriteMany (RWX) persistent volumes out of the box. This means multiple pods and VMs can mount the same volume...
Starting with Cozystack v1.0, you can use ReadWriteMany (RWX) persistent volumes out of the box. This means multiple pods and VMs can mount the same volume simultaneously — a capability essential for shared filesystems, multi-replica applications, and cross-VM data sharing.
Under the hood, the kubevirt-csi-driver provisions a dedicated NFS server for each RWX PVC, backed by DRBD-replicated (LINSTOR) block storage, with CiliumNetworkPolicy handling traffic isolation. For tenants, it’s as simple as creating a standard PVC with accessModes: [ReadWriteMany] and storageClassName: nfs.
Update (September 2026, Cozystack v1.6): on the management cluster, RWX volumes must sit on a DRBD-backed LINSTOR StorageClass — linstor-csi rejects RWX on non-DRBD classes. Mounting an existing external NFS export instead is handled by the optional cozystack.nfs-driver package (csi-driver-nfs). See the current storage documentation.
What this unlocks:
→ Multi-replica deployments sharing persistent state
→ Shared data across multiple VMs in tenant Kubernetes clusters
→ Volume snapshots, expansion, and cloning — all supported per volume
→ No external NFS infrastructure needed — everything runs inside Cozystack
What is Cozystack? Cozystack is a free and open-source PaaS platform and framework for building clouds. It enables you to run a full-featured cloud platform on bare metal with managed Kubernetes, VMs, databases, and storage — all powered by proven CNCF technologies like Talos Linux, KubeVirt, Flux CD, and LINSTOR.
Starting from which Cozystack version are RWX (ReadWriteMany) volumes supported out of the box?
Why: Starting with Cozystack v1.0, you can use ReadWriteMany (RWX) persistent volumes out of the box. Multiple pods and VMs can mount the same volume simultaneously.
Question 2 / 5
What technology stack powers RWX under the hood?
Why: The kubevirt-csi-driver provisions a dedicated NFS server for each RWX PVC, backed by DRBD-replicated (LINSTOR) block storage. CiliumNetworkPolicy handles traffic isolation between tenants.
Question 3 / 5
How does a tenant request an RWX volume?
Why: Tenants create a standard PVC with accessModes: [ReadWriteMany] and storageClassName: nfs. No external NFS infrastructure needed — everything runs inside Cozystack.
Question 4 / 5
Which use case is NOT named as unlocked by RWX?
Why: RWX unlocks: multi-replica deployments sharing persistent state; shared data across multiple VMs in tenant K8s clusters; volume snapshots, expansion, and cloning per volume; no external NFS infrastructure needed. GPU live migration is an unrelated industry-wide limitation.
Question 5 / 5
How does the article describe what Cozystack is, in this announcement?
Why: The boilerplate: Cozystack is a free and open-source PaaS platform and framework for building clouds. Runs full-featured cloud on bare metal with managed Kubernetes, VMs, databases, and storage — powered by proven CNCF technologies (Talos, KubeVirt, Flux CD, LINSTOR).
