title: GCE persistent disk bursting and throttling metrics
body: <p>Google Cloud Platform/Compute Engine (GCP/GCE) standard persistent disks are stated to have up to 0.12 MB/s sustained read throughput per GB (<a href="https://cloud.google.com/compute/docs/disks/" rel="nofollow noreferrer">ref</a>). I know bursting exists, but its specific behavior isn't described anywhere.</p>
  
  <p>The <code>instance/disk/throttled_read_bytes_count</code> metric is described as the "Delta count of bytes in throttled read operations" (<a href="https://cloud.google.com/monitoring/api/metrics_gcp" rel="nofollow noreferrer">ref</a>). <strong>If that value is zero, does that mean that increasing the size of our disk won't improve our application's performance?</strong> -- i.e. that our disk read needs are 100% satisfied by the current max throughput + bursting?</p>
  
  <p>(There's also a metric for read_ops, which is zero in our case as well.)</p>