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 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.

Documentation: https://cozystack.io/docs/v1.6/storage/nfs/ Feature PR: https://github.com/cozystack/cozystack/pull/2042

— - Website: https://cozystack.io GitHub: https://github.com/cozystack/cozystack

RWX (ReadWriteMany) volumes in Cozystack — native shared storage for your workloads was originally published in Ænix on Medium, where people are continuing the conversation by highlighting and responding to this story.