@Override
  protected AdminResponse createResponse(DistributionManager dm) {
    HashSet<PersistentID> persistentIds;
    try {
      persistentIds = prepareBackupFactory
          .createPrepareBackup(dm.getDistributionManagerId(), dm.getCache(), properties).run();
    } catch (IOException | InterruptedException e) {
      logger.error(String.format("Error processing request %s.", getClass()), e);
      return AdminFailureResponse.create(getSender(), e);
    }
    return prepareBackupFactory.createBackupResponse(getSender(), persistentIds);
  }
A request to from an admin VM to all non admin members to start a backup. In the prepare phase of
the backup, the members will suspend bucket destroys to make sure buckets aren't missed during
the backup.
geode-core/src/main/java/org/apache/geode/internal/cache/backup/PrepareBackupRequest.java