Rook: Deployment 3 replicas - Volume is already attached by pod (second and third replicas)

[gustavomr]

Trying to create a deployment (with 3 replicas) with PVC. The first pod attached to PVC sucessfully.

The second and third pod shows the same error:

MountVolume.SetUp failed for volume "pvc-ed04a6ce-8b7f-11e8-ab36-08002759a5f7" : mount command failed, status: Failure, reason: Rook: Mount volume failed: failed to attach volume pvc-ed04a6ce-8b7f-11e8-ab36-08002759a5f7 for pod default/nginx-deployment-86dfb99868-n82x8. Volume is already attached by pod default/nginx-deployment-86dfb99868-szpkd. Status Running

Using Kubernetes 1.11 and Centos 7.

[jbw976]

Hi @gustavomr, the volumes provisioned and mounted by rook-ceph-block are ReadWriteOnce meaning they can not have more than one writer attach to the same volume. See https://github.com/rook/rook/blob/release-0.8/cluster/examples/kubernetes/mysql.yaml#L24.

Were you intending for them all to access/share the same volume? If so, you could look at using a shared filesystem instead: https://rook.io/docs/rook/v0.8/filesystem.html

If you want the 3 replicas to each get their own volume, you could consider using a StatefulSet instead that has a volumeClaimTemplate. Specifying the rook-ceph-block storage class in that template would get 3 separate volumes created for you. More details: https://kubernetes.io/docs/concepts/workloads/controllers/statefulset/

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[amaczuga]

I am observing this behavior with RWX access mode claims. Rook 0.8.