diff --git a/staffeln/conductor/backup.py b/staffeln/conductor/backup.py
index 8394187..9f3f54d 100755
--- a/staffeln/conductor/backup.py
+++ b/staffeln/conductor/backup.py
@@ -227,7 +227,7 @@
             return False
 
     #  delete all backups forcily regardless of the status
-    def hard_remove_volume_backup(self, backup_object):
+    def hard_remove_volume_backup(self, backup_object, skip_inc_err=False):
         try:
             project_id = backup_object.project_id
             if project_id not in self.project_list:
@@ -251,16 +251,19 @@
             backup_object.delete_backup()
 
         except Exception as e:
-            LOG.warn(
-                _(
-                    "Backup %s deletion failed. Need to delete manually."
-                    "%s" % (backup_object.backup_id, str(e))
+            if skip_inc_err and "Incremental backups exist for this backup" in str(e):
+                pass
+            else:
+                LOG.warn(
+                    _(
+                        "Backup %s deletion failed. Need to delete manually."
+                        "%s" % (backup_object.backup_id, str(e))
+                    )
                 )
-            )
 
-            # TODO(Alex): Add it into the notification queue
-            # remove from the backup table
-            backup_object.delete_backup()
+                # TODO(Alex): Add it into the notification queue
+                # remove from the backup table
+                backup_object.delete_backup()
 
     def update_project_list(self):
         projects = self.openstacksdk.get_projects()
diff --git a/staffeln/conductor/manager.py b/staffeln/conductor/manager.py
index a105fc1..33ab139 100755
--- a/staffeln/conductor/manager.py
+++ b/staffeln/conductor/manager.py
@@ -238,8 +238,11 @@
                         and not self.instance_retention_map
                     ):
                         return
-                    retention_backups = []
                     backup_instance_map = {}
+
+                    # get project list
+                    self.controller.update_project_list()
+
                     for backup in self.get_backup_list():
                         # Create backup instance map for later sorted by created_at.
                         # This can be use as base of judgement on delete a backup.
@@ -252,67 +255,18 @@
                             backup_instance_map[backup.instance_id] = [backup]
 
                     # Sort backup instance map and use it to check backup create time and order.
-                    # Generate retention_backups base on it.
                     for instance_id in backup_instance_map:
                         sorted_backup_list = sorted(
                             backup_instance_map[instance_id],
                             key=lambda backup: backup.created_at.timestamp(),
                             reverse=True,
                         )
-                        idx = 0
-                        list_len = len(sorted_backup_list)
-                        find_earlier_full = False
-                        purge_incremental = True
-
-                        while idx < list_len:
-                            backup = sorted_backup_list[idx]
-                            if find_earlier_full and backup.incremental is True:
-                                # Skip on incrementals when try to find earlier
-                                # created full backup.
-                                idx += 1
-                                continue
-                            # If we should consider delete this backup
+                        for backup in sorted_backup_list:
                             if self.is_retention(backup):
-                                # If is full backup
-                                if not backup.incremental:
-                                    # For full backup should be deleted, purge
-                                    # all backup include itself, otherwise, purge
-                                    # only all earlier one if other backup depends on it.
-                                    if not purge_incremental:
-                                        # Still got incremental dependency,
-                                        # but add all backups older than this one if any.
-                                        idx += 1
-                                    retention_backups += sorted_backup_list[idx:]
-                                    break
-                                # If is incremental backup
-                                else:
-                                    # This means there still have incremental
-                                    # backup denepds on this one. So we will go to the
-                                    # latest incremental backup for earlier full backup,
-                                    # or to the earlier full backup itself if it had no
-                                    # incremental backup rely on.
-                                    if not purge_incremental:
-                                        find_earlier_full = True
-                                        idx += 1
-                                    else:
-                                        # The later backup is full backup, fine for us to
-                                        # purge this and all older backup.
-                                        retention_backups += sorted_backup_list[idx:]
-                                        break
-                            else:
-                                # If it's incremental and not to be delete, make sure
-                                # we keep all it's dependency.
-                                purge_incremental = (
-                                    False if backup.incremental else True
+                                # Try to delete and skip any incremental exist error.
+                                self.controller.hard_remove_volume_backup(
+                                    backup, skip_inc_err=True
                                 )
-                                idx += 1
-
-                    if not retention_backups:
-                        return
-                    # 2. get project list
-                    self.controller.update_project_list()
-                    # 3. remove the backups
-                    self.remove_backups(retention_backups)
             except coordination.LockAcquireFailed:
                 LOG.debug("Failed to lock for retention")