diff --git a/src/config.cc b/src/config.cc
index 894b3b48227..1fcb92ca2ca 100644
--- a/src/config.cc
+++ b/src/config.cc
@@ -450,6 +450,7 @@ static struct config_option config_optionsp[] = {
 	OPTION(mds_bal_split_size, 0, OPT_INT, 10000),
 	OPTION(mds_bal_split_rd, 0, OPT_FLOAT, 25000),
 	OPTION(mds_bal_split_wr, 0, OPT_FLOAT, 10000),
+	OPTION(mds_bal_split_bits, 0, OPT_INT, 3),
 	OPTION(mds_bal_merge_size, 0, OPT_INT, 50),
 	OPTION(mds_bal_merge_rd, 0, OPT_FLOAT, 1000),
 	OPTION(mds_bal_merge_wr, 0, OPT_FLOAT, 1000),
diff --git a/src/config.h b/src/config.h
index c6f5214894c..3141b9e61bb 100644
--- a/src/config.h
+++ b/src/config.h
@@ -275,6 +275,7 @@ struct md_config_t {
   int mds_bal_split_size;
   float mds_bal_split_rd;
   float mds_bal_split_wr;
+  int mds_bal_split_bits;
   int mds_bal_merge_size;
   float mds_bal_merge_rd;
   float mds_bal_merge_wr;
diff --git a/src/mds/MDBalancer.cc b/src/mds/MDBalancer.cc
index 29e1de4a917..609e16f517d 100644
--- a/src/mds/MDBalancer.cc
+++ b/src/mds/MDBalancer.cc
@@ -328,7 +328,7 @@ void MDBalancer::do_fragmenting()
     if (!dir->is_auth()) continue;
 
     dout(0) << "do_fragmenting splitting " << *dir << dendl;
-    mds->mdcache->split_dir(dir, 4);
+    mds->mdcache->split_dir(dir, g_conf.mds_bal_split_bits);
   }
   split_queue.clear();
 }