Alertmanager silence storage on persistent volume claim with jsonnet

[roelandvanbatenburg]

We don't need HA for alertmanager, but we do want to persist the silences we have. I have found prometheus/alertmanager#1673 (comment) and #1014 that point in the right direction, but I cannot find out how to configure this with jsonnet.

I have tried this:

{
  alertmanager+: {
    alertmanager+: {
      spec+: {
        volumeMounts: [
          {
            name: "alertmanager-data",
            mountPath: "/alertmanager"
          },
        ],
        storage: {
          volumeClaimTemplate: {
            metadata: {
              name: "alertmanager-data"
            },
            spec: {
              accessModes: ["ReadWriteOnce"],
              resources: {
                requests: {
                  storage: "10Mi"
                },
              },
            },
          },
        },
      },
    },
  },

But then I get the error

  Warning  FailedCreate  20s (x13 over 40s)  statefulset-controller  create Pod alertmanager-main-0 in StatefulSet alertmanager-main failed error: Pod "alertmanager-main-0" is invalid: spec.containers[0].volumeMounts[3].mountPath: Invalid value: "/alertmanager": must be unique

Which makes sense as /alertmanager is already specified as a

        - mountPath: /alertmanager
          name: alertmanager-data
          subPath: alertmanager-db

I think this is done by the prometheus-operator, but I do not know how to disable this. Or am I on the wrong path entirely?

Thanks in advance!