void initializeFailedDiskCount(final StorageManager storageManager) {
    Gauge<Integer> failedDiskCount = storageManager::getFailedDiskCount;
    registry.gauge(MetricRegistry.name(StorageManager.class, "FailedDisksCount"), () -> failedDiskCount);
  }
Initialized gauge that track the number of failed disks.
@param storageManager The {@link StorageManager} instance.
ambry-store/src/main/java/com/github/ambry/store/StorageManagerMetrics.java