CKA Storage Practice Question
A pod uses a PVC with access mode RWO. The pod is scheduled on node A. You want to schedule another pod on node B that uses the same PVC. What will happen?
⚠ Common exam trap
Test-takers frequently confuse access modes with pod-level permissions, assuming 'ReadWriteOnce' means the volume can be mounted by multiple pods as long as they are on the same node, or that the second pod will mount as read-only, when in fact the restriction is node-based and enforced at the storage layer.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The second pod will be stuck in ContainerCreating state until the first pod releases the volume
A PVC with access mode RWO (ReadWriteOnce) can only be mounted as a block device or filesystem by a single node at a time. When the first pod on node A has the volume attached, the second pod on node B cannot attach the same volume because the underlying storage (e.g., an AWS EBS volume or GCE Persistent Disk) does not support multi-node attachment. The second pod will remain in ContainerCreating state with a 'Multi-Attach error' until the first pod releases the volume (e.g., by being deleted or rescheduled).
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
The second pod will be stuck in ContainerCreating state until the first pod releases the volume
Why this is correct
When a PersistentVolume is bound using ReadWriteOnce (RWO), it can only be mounted by a single node at any given time. If a second pod is scheduled to a different node and attempts to use the same PVC, the volume attachment controller will block the attachment to prevent data corruption. Consequently, the second pod remains stuck in the ContainerCreating state, generating Multi-Attach error events until the first pod is deleted and the volume is fully detached from its node.
- ✗
Both pods will mount the volume and share it without issues
Why it's wrong here
This behavior is impossible under the ReadWriteOnce access mode, which strictly restricts volume mounting to a single node at a time. To allow multiple pods on different nodes to concurrently mount and share a single volume, the PersistentVolume must support and be configured with the ReadWriteMany (RWX) access mode. Attempting this with RWO will result in attachment failures for any subsequent nodes.
- ✗
The second pod will successfully mount the volume as read-only
Why it's wrong here
Kubernetes does not dynamically downgrade or alter access modes to allow secondary read-only mounts on different nodes. The ReadWriteOnce restriction is enforced at the infrastructure or block-storage level, meaning no secondary node can attach the volume in any capacity, read-only or otherwise, while it is actively attached to the first node. To achieve multi-node read-only access, the volume must be provisioned with ReadOnlyMany (ROX).
- ✗
The first pod will be evicted to allow the second pod to use the volume
Why it's wrong here
The Kubernetes control plane prioritizes workload stability and will never automatically evict a healthy, running pod to resolve a volume attachment conflict for a newly scheduled pod. The scheduler assumes the existing workload has a valid claim on the resource, leaving the second pod to wait indefinitely in a blocked state. Resolving this conflict requires manual intervention, such as scaling down the first deployment or adjusting node affinity.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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