By default a Portworx volume can be attached to a single pod only.
If you have applications that need to run more than one instance attaching to the same PVC and you are seeing an error similar to below when deploying:
MountVolume.SetUp failed for volume "pvc-c85f2297-7cca-11e9-b839-1259e1dd1832" : Volume is attached on another node
Then you have to create the volume as a shared volume.
You can read more details and see examples on the documentation link below: