How do I control a kubernetes PersistentVolumeClaim to bind to a specific PersistentVolume?

Question

I have multiple volumes and one claim. How can I tell the claim to which volume to bind to?

How does a PersistentVolumeClaim know to which volume to bind? Can I controls this using some other parameters or metadata?

I have the following PersistentVolumeClaim:

{                                                                                                                 
    "apiVersion": "v1",                                                                                           
    "kind": "PersistentVolumeClaim",                                                                              
    "metadata": {                                                                                                 
        "name": "default-drive-claim"                                                                             
    },                                                                                                            
    "spec": {                                                                                                     
        "accessModes": [                                                                                          
            "ReadWriteOnce"                                                                                       
        ],                                                                                                        
        "resources": {                                                                                            
            "requests": {                                                                                         
                "storage": "10Gi"                                                                                 
            }                                                                                                     
        }                                                                                                         
    }                                                                                                             
}

{                                                                                                                 
    "apiVersion": "v1",                                                                                           
    "kind": "PersistentVolume",
    "metadata": {                                                                                                 
        "name": "default-drive-disk",                                                                             
        "labels": {                                                                                               
             "name": "default-drive-disk"                                                                         
        }
    },      
    "spec": {                                                                                                     
        "capacity": {
            "storage": "10Gi"                                                                                     
        },      
        "accessModes": [                                                                                          
            "ReadWriteOnce"                                                                                       
        ],                                                                                                        
        "gcePersistentDisk": {                                                                                    
            "pdName": "a1-drive",
            "fsType": "ext4"
        }
    }
}

If I create the claim and the volume using:

kubectl create -f pvc.json -f pv.json

I get the following listing of the volumes and claims:

NAME                 LABELS                    CAPACITY   ACCESSMODES   STATUS    CLAIM                         REASON    AGE
default-drive-disk   name=default-drive-disk   10Gi       RWO           Bound     default/default-drive-claim             2s
NAME                  LABELS    STATUS    VOLUME               CAPACITY   ACCESSMODES   AGE
default-drive-claim   <none>    Bound     default-drive-disk   10Gi       RWO           2s

How does the claim know to which volume to bind?

Answer 1

The current implementation does not allow your PersistentVolumeClaim to target specific PersistentVolumes. Claims bind to volumes based on its capabilities (access modes) and capacity.

In the works is the next iteration of PersistentVolumes, which includes a PersistentVolumeSelector on the claim. This would work exactly like a NodeSelector on Pod works. The volume would have to match the label selector in order to bind. This is the targeting you are looking for.

Please see https://github.com/kubernetes/kubernetes/pull/17056 for the proposal containing PersistentVolumeSelector.