public DiskManager getDiskManager(PartitionId id) {
    return partitionToDiskManager.get(id);
  }
@param id the {@link PartitionId} to find the DiskManager for.
@return the {@link DiskManager} corresponding to the given {@link PartitionId}, or {@code null} if no DiskManager was found for
        that partition
ambry-store/src/main/java/com/github/ambry/store/StorageManager.java