// 2. Do transitions
      // Each storage directory is treated individually.
      // During startup some of them can upgrade or roll back
      // while others could be up-to-date for the regular startup.
// 2. Do transitions
      // Each storage directory is treated individually.
      // During startup some of them can upgrade or roll back
      // while others could be up-to-date for the regular startup. | BlockPoolSliceStorage.java