AWS EKS instance not found when attaching EBS volume

Question

A few days ago attaching EBS volumes suddenly stopped working.
My EKS cluster uses ebs.csi.aws.com addon with dynamic provisioning.

here is my storageClass config

```
kind: StorageClass
apiVersion: storage.k8s.io/v1
metadata:
  name: ebs-sc
provisioner: ebs.csi.aws.com
parameters:
  type: gp3
reclaimPolicy: Delete
volumeBindingMode: WaitForFirstConsumer
```

and volumeClaimTemplate in my sts config

```
  volumeClaimTemplates:
  - metadata:
      name: log
    spec:
      accessModes: [ "ReadWriteOnce" ]
      resources:
        requests:
          storage: 1Gi
```

after sts deployment a PVC, PV and VolumeAttachment are created, however the pod is stuck in ContainerCreating state with error AttachVolume.Attach failed for volume "pvc-xxx" : rpc error: code = NotFound desc = Instance "i-xxx" not found

I triple-checked, the volume is not attached to any other instance, and the instance exists.

One funny thing though - when I describe the created PV I see this
```
Source:
    Type:              CSI (a Container Storage Interface (CSI) volume source)
    Driver:            ebs.csi.aws.com
    FSType:            ext4
    VolumeHandle:      vol-xxx
    ReadOnly:          false
    VolumeAttributes:      storage.kubernetes.io/csiProvisionerIdentity=xxx-8081-ebs.csi.aws.com
```

the (unmasked) volumeHandle does not even exist.

Where might be the problem? As I said earlier, this issue popped up from day to day without changing the config

K8S version 1.24
EBS CSI Driver addon version v1.11.5-eksbuild.2 (upgrade nor downgrade didn't help)

Thanks

Answer

When you use EBS for persistent volumes, you need remebmer, that EBS is located in a single AZ, so only EC2 instance from the same AZ will be able to attach it. If a pod is rescheduled to a node in another AZ, it may fail with an error that it can not find/attach a persistent volume. 
Every node can have a label with its AZ, so you can use nodeSelector or Affinity to make pod be scheduled only in particular AZ

AWS EKS instance not found when attaching EBS volume

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