code: private DB openStorage(StorageType storageType) {
          DB storage = storageRegistry.get(storageType);
          if(!isOpenStorage(storage)) {
              DBMaker m;
              if(storageType == StorageType.PRIMARY_STORAGE || storageType == StorageType.SECONDARY_STORAGE) {
                  //main storage
                  Path rootPath = getRootPath(storageName);
                  try {
                      createDirectoryIfNotExists(rootPath);
                  }
                  catch (IOException ex) {
                      throw new UncheckedIOException(ex);
                  }
  
                  m = DBMaker.newFileDB(new File(rootPath.toFile(), storageType.toString()));
              }
              else if(storageType == StorageType.TEMP_PRIMARY_STORAGE || storageType == StorageType.TEMP_SECONDARY_STORAGE) {
                  //temporary storage
                  m = DBMaker.newTempFileDB().deleteFilesAfterClose();
              }
              else {
                  throw new IllegalArgumentException("Unsupported StorageType.");
              }
              
              if(storageConfiguration.isCompressed()) {
                  m = m.compressionEnable();
              }
  
              boolean permitCaching = storageType == StorageType.PRIMARY_STORAGE || storageType == StorageType.TEMP_PRIMARY_STORAGE;
              if(permitCaching && storageConfiguration.getCacheSize()>0) {
                  m = m.cacheLRUEnable().cacheSize(storageConfiguration.getCacheSize()) ;
              }
              else {
                  m = m.cacheDisable();
              }
  
              if(storageConfiguration.isAsynchronous()) {
                  m = m.asyncWriteEnable();
              }
              
              m = m.transactionDisable();
              
              m = m.closeOnJvmShutdown();
              
              storage = m.make();
              storageRegistry.put(storageType, storage);
          }
          return storage;
      }
docs: Opens the storage (if not already open) and returns the storage object.
  
  @param storageType
  @return