diff --git a/buildheader/make_tdb.cc b/buildheader/make_tdb.cc
index 4de60a354ad..20150c59fff 100644
--- a/buildheader/make_tdb.cc
+++ b/buildheader/make_tdb.cc
@@ -540,6 +540,9 @@ static void print_db_struct (void) {
 			 "int (*change_compression_method)(DB*,TOKU_COMPRESSION_METHOD)",
 			 "int (*get_compression_method)(DB*,TOKU_COMPRESSION_METHOD*)",
 			 "int (*set_compression_method)(DB*,TOKU_COMPRESSION_METHOD)",
+			 "int (*change_fanout)(DB *db, uint32_t fanout)",
+			 "int (*get_fanout)(DB *db, uint32_t *fanout)",
+			 "int (*set_fanout)(DB *db, uint32_t fanout)",
 			 "int (*set_indexer)(DB*, DB_INDEXER*)",
 			 "void (*get_indexer)(DB*, DB_INDEXER**)",
 			 "int (*verify_with_progress)(DB *, int (*progress_callback)(void *progress_extra, float progress), void *progress_extra, int verbose, int keep_going)",
diff --git a/ft/ft-flusher.cc b/ft/ft-flusher.cc
index 9d7369accd5..9440573976f 100644
--- a/ft/ft-flusher.cc
+++ b/ft/ft-flusher.cc
@@ -544,11 +544,13 @@ ct_flusher_advice_init(struct flusher_advice *fa, struct flush_status_update_ext
 // a leaf node that is not entirely in memory. If so, then
 // we cannot be sure if the node is reactive.
 //
-static bool may_node_be_reactive(FTNODE node)
+static bool may_node_be_reactive(FT ft, FTNODE node)
 {
-    if (node->height == 0) return true;
+    if (node->height == 0) {
+        return true;
+    }
     else {
-        return (get_nonleaf_reactivity(node) != RE_STABLE);
+        return (get_nonleaf_reactivity(node, ft->h->fanout) != RE_STABLE);
     }
 }
 
@@ -1589,7 +1591,7 @@ static void ft_flush_some_child(
     // Let's do a quick check to see if the child may be reactive
     // If the child cannot be reactive, then we can safely unlock
     // the parent before finishing reading in the entire child node.
-    bool may_child_be_reactive = may_node_be_reactive(child);
+    bool may_child_be_reactive = may_node_be_reactive(ft, child);
 
     paranoid_invariant(child->thisnodename.b!=0);
     //VERIFY_NODE(brt, child);
@@ -1631,7 +1633,7 @@ static void ft_flush_some_child(
     // we wont be splitting/merging child
     // and we have already replaced the bnc
     // for the root with a fresh one
-    enum reactivity child_re = get_node_reactivity(child, ft->h->nodesize);
+    enum reactivity child_re = get_node_reactivity(ft, child);
     if (parent && child_re == RE_STABLE) {
         toku_unpin_ftnode_off_client_thread(ft, parent);
         parent = NULL;
@@ -1661,7 +1663,7 @@ static void ft_flush_some_child(
     // let's get the reactivity of the child again,
     // it is possible that the flush got rid of some values
     // and now the parent is no longer reactive
-    child_re = get_node_reactivity(child, ft->h->nodesize);
+    child_re = get_node_reactivity(ft, child);
     // if the parent has been unpinned above, then
     // this is our only option, even if the child is not stable
     // if the child is not stable, we'll handle it the next
@@ -1971,7 +1973,7 @@ void toku_ft_flush_node_on_background_thread(FT h, FTNODE parent)
         //
         // successfully locked child
         //
-        bool may_child_be_reactive = may_node_be_reactive(child);
+        bool may_child_be_reactive = may_node_be_reactive(h, child);
         if (!may_child_be_reactive) {
             // We're going to unpin the parent, so before we do, we must
             // check to see if we need to blow away the basement nodes to
diff --git a/ft/ft-internal.h b/ft/ft-internal.h
index b02c250fb9e..cc7a708d518 100644
--- a/ft/ft-internal.h
+++ b/ft/ft-internal.h
@@ -117,15 +117,10 @@ PATENT RIGHTS GRANT:
 #include <util/omt.h>
 #include "bndata.h"
 
-#ifndef FT_FANOUT
-#define FT_FANOUT 16
-#endif
-enum { TREE_FANOUT = FT_FANOUT };
 enum { KEY_VALUE_OVERHEAD = 8 }; /* Must store the two lengths. */
-enum { FT_CMD_OVERHEAD = (2 + sizeof(MSN))     // the type plus freshness plus MSN
-};
-
-enum { FT_DEFAULT_NODE_SIZE = 1 << 22 };
+enum { FT_CMD_OVERHEAD = (2 + sizeof(MSN)) };   // the type plus freshness plus MSN
+enum { FT_DEFAULT_FANOUT = 16 };
+enum { FT_DEFAULT_NODE_SIZE = 4 * 1024 * 1024 };
 enum { FT_DEFAULT_BASEMENT_NODE_SIZE = 128 * 1024 };
 
 //
@@ -238,12 +233,10 @@ void toku_bnc_flush_to_child(FT h, NONLEAF_CHILDINFO bnc, FTNODE child, TXNID ol
 bool toku_bnc_should_promote(FT ft, NONLEAF_CHILDINFO bnc) __attribute__((const, nonnull));
 bool toku_ft_nonleaf_is_gorged(FTNODE node, uint32_t nodesize);
 
-
-enum reactivity get_nonleaf_reactivity (FTNODE node);
-enum reactivity get_node_reactivity (FTNODE node, uint32_t nodesize);
+enum reactivity get_nonleaf_reactivity(FTNODE node, unsigned int fanout);
+enum reactivity get_node_reactivity(FT ft, FTNODE node);
 uint32_t get_leaf_num_entries(FTNODE node);
 
-
 // data of an available partition of a leaf ftnode
 struct ftnode_leaf_basement_node {
     bn_data data_buffer;
@@ -336,7 +329,7 @@ struct ftnode {
     int    height; /* height is always >= 0.  0 for leaf, >0 for nonleaf. */
     int    dirty;
     uint32_t fullhash;
-    int n_children; //for internal nodes, if n_children==TREE_FANOUT+1 then the tree needs to be rebalanced.
+    int n_children; //for internal nodes, if n_children==fanout+1 then the tree needs to be rebalanced.
                     // for leaf nodes, represents number of basement nodes
     unsigned int    totalchildkeylens;
     DBT *childkeys;   /* Pivot keys.  Child 0's keys are <= childkeys[0].  Child 1's keys are <= childkeys[1].
@@ -509,6 +502,7 @@ struct ft_header {
     unsigned int nodesize; 
     unsigned int basementnodesize;
     enum toku_compression_method compression_method;
+    unsigned int fanout;
 
     // Current Minimum MSN to be used when upgrading pre-MSN BRT's.
     // This is decremented from our currnt MIN_MSN so as not to clash
@@ -590,6 +584,7 @@ struct ft_options {
     unsigned int nodesize;
     unsigned int basementnodesize;
     enum toku_compression_method compression_method;
+    unsigned int fanout;
     unsigned int flags;
     ft_compare_func compare_fun;
     ft_update_func update_fun;
diff --git a/ft/ft-ops.cc b/ft/ft-ops.cc
index 452a0e09e2e..617a0ddc1d7 100644
--- a/ft/ft-ops.cc
+++ b/ft/ft-ops.cc
@@ -428,21 +428,21 @@ get_leaf_reactivity (FTNODE node, uint32_t nodesize) {
 }
 
 enum reactivity
-get_nonleaf_reactivity (FTNODE node) {
+get_nonleaf_reactivity(FTNODE node, unsigned int fanout) {
     paranoid_invariant(node->height>0);
     int n_children = node->n_children;
-    if (n_children > TREE_FANOUT) return RE_FISSIBLE;
-    if (n_children*4 < TREE_FANOUT) return RE_FUSIBLE;
+    if (n_children > (int) fanout) return RE_FISSIBLE;
+    if (n_children*4 < (int) fanout) return RE_FUSIBLE;
     return RE_STABLE;
 }
 
 enum reactivity
-get_node_reactivity (FTNODE node, uint32_t nodesize) {
+get_node_reactivity(FT ft, FTNODE node) {
     toku_assert_entire_node_in_memory(node);
     if (node->height==0)
-        return get_leaf_reactivity(node, nodesize);
+        return get_leaf_reactivity(node, ft->h->nodesize);
     else
-        return get_nonleaf_reactivity(node);
+        return get_nonleaf_reactivity(node, ft->h->fanout);
 }
 
 unsigned int
@@ -2689,7 +2689,7 @@ static bool process_maybe_reactive_child(FT ft, FTNODE parent, FTNODE child, int
 //  true if relocking is needed
 //  false otherwise
 {
-    enum reactivity re = get_node_reactivity(child, ft->h->nodesize);
+    enum reactivity re = get_node_reactivity(ft, child);
     enum reactivity newre;
     BLOCKNUM child_blocknum;
     uint32_t child_fullhash;
@@ -2723,7 +2723,7 @@ static bool process_maybe_reactive_child(FT ft, FTNODE parent, FTNODE child, int
             child_blocknum = BP_BLOCKNUM(newparent, childnum);
             child_fullhash = compute_child_fullhash(ft->cf, newparent, childnum);
             toku_pin_ftnode_off_client_thread_batched(ft, child_blocknum, child_fullhash, &bfe, PL_WRITE_CHEAP, 1, &newparent, &newchild);
-            newre = get_node_reactivity(newchild, ft->h->nodesize);
+            newre = get_node_reactivity(ft, newchild);
             if (newre == RE_FISSIBLE) {
                 enum split_mode split_mode;
                 if (newparent->height == 1 && (loc & LEFT_EXTREME) && childnum == 0) {
@@ -2769,7 +2769,7 @@ static bool process_maybe_reactive_child(FT ft, FTNODE parent, FTNODE child, int
             child_blocknum = BP_BLOCKNUM(newparent, childnum);
             child_fullhash = compute_child_fullhash(ft->cf, newparent, childnum);
             toku_pin_ftnode_off_client_thread_batched(ft, child_blocknum, child_fullhash, &bfe, PL_READ, 1, &newparent, &newchild);
-            newre = get_node_reactivity(newchild, ft->h->nodesize);
+            newre = get_node_reactivity(ft, newchild);
             if (newre == RE_FUSIBLE && newparent->n_children >= 2) {
                 toku_unpin_ftnode_read_only(ft, newchild);
                 toku_ft_merge_child(ft, newparent, childnum);
@@ -3059,7 +3059,7 @@ void toku_ft_root_put_cmd(
     // injection thread to change lock type back and forth, when only one
     // of them needs to in order to handle the split.  That's not great,
     // but root splits are incredibly rare.
-    enum reactivity re = get_node_reactivity(node, ft->h->nodesize);
+    enum reactivity re = get_node_reactivity(ft, node);
     switch (re) {
     case RE_STABLE:
     case RE_FUSIBLE: // cannot merge anything at the root
@@ -3429,6 +3429,7 @@ int toku_open_ft_handle (const char *fname, int is_create, FT_HANDLE *ft_handle_
     toku_ft_handle_set_nodesize(brt, nodesize);
     toku_ft_handle_set_basementnodesize(brt, basementnodesize);
     toku_ft_handle_set_compression_method(brt, compression_method);
+    toku_ft_handle_set_fanout(brt, 16);
     toku_ft_set_bt_compare(brt, compare_fun);
 
     int r = toku_ft_handle_open(brt, fname, is_create, only_create, cachetable, txn);
@@ -3516,6 +3517,27 @@ toku_ft_handle_get_compression_method(FT_HANDLE t, enum toku_compression_method
     }
 }
 
+void
+toku_ft_handle_set_fanout(FT_HANDLE ft_handle, unsigned int fanout)
+{
+    if (ft_handle->ft) {
+        toku_ft_set_fanout(ft_handle->ft, fanout);
+    }
+    else {
+        ft_handle->options.fanout = fanout;
+    }
+}
+
+void
+toku_ft_handle_get_fanout(FT_HANDLE ft_handle, unsigned int *fanout)
+{
+    if (ft_handle->ft) {
+        toku_ft_get_fanout(ft_handle->ft, fanout);
+    }
+    else {
+        *fanout = ft_handle->options.fanout;
+    }
+}
 static int
 verify_builtin_comparisons_consistent(FT_HANDLE t, uint32_t flags) {
     if ((flags & TOKU_DB_KEYCMP_BUILTIN) && (t->options.compare_fun != toku_builtin_compare_fun))
@@ -3582,6 +3604,7 @@ toku_ft_handle_inherit_options(FT_HANDLE t, FT ft) {
         .nodesize = ft->h->nodesize,
         .basementnodesize = ft->h->basementnodesize,
         .compression_method = ft->h->compression_method,
+        .fanout = ft->h->fanout,
         .flags = ft->h->flags,
         .compare_fun = ft->compare_fun,
         .update_fun = ft->update_fun
@@ -3937,6 +3960,7 @@ void toku_ft_handle_create(FT_HANDLE *ft_handle_ptr) {
     brt->options.nodesize = FT_DEFAULT_NODE_SIZE;
     brt->options.basementnodesize = FT_DEFAULT_BASEMENT_NODE_SIZE;
     brt->options.compression_method = TOKU_DEFAULT_COMPRESSION_METHOD;
+    brt->options.fanout = FT_DEFAULT_FANOUT;
     brt->options.compare_fun = toku_builtin_compare_fun;
     brt->options.update_fun = NULL;
     *ft_handle_ptr = brt;
diff --git a/ft/ft-ops.h b/ft/ft-ops.h
index 34ca6586c62..ff7a3708f3d 100644
--- a/ft/ft-ops.h
+++ b/ft/ft-ops.h
@@ -137,6 +137,8 @@ void toku_ft_handle_set_basementnodesize(FT_HANDLE, unsigned int basementnodesiz
 void toku_ft_handle_get_basementnodesize(FT_HANDLE, unsigned int *basementnodesize);
 void toku_ft_handle_set_compression_method(FT_HANDLE, enum toku_compression_method);
 void toku_ft_handle_get_compression_method(FT_HANDLE, enum toku_compression_method *);
+void toku_ft_handle_set_fanout(FT_HANDLE, unsigned int fanout);
+void toku_ft_handle_get_fanout(FT_HANDLE, unsigned int *fanout);
 
 void toku_ft_set_bt_compare(FT_HANDLE, ft_compare_func);
 ft_compare_func toku_ft_get_bt_compare (FT_HANDLE brt);
diff --git a/ft/ft-serialize.cc b/ft/ft-serialize.cc
index 8afdb9e4beb..e6fbe0a2ce4 100644
--- a/ft/ft-serialize.cc
+++ b/ft/ft-serialize.cc
@@ -404,6 +404,7 @@ int deserialize_ft_versioned(int fd, struct rbuf *rb, FT *ftp, uint32_t version)
             .nodesize = nodesize,
             .basementnodesize = basementnodesize,
             .compression_method = compression_method,
+            .fanout = FT_DEFAULT_FANOUT, // fanout is not serialized, must be set at startup
             .highest_unused_msn_for_upgrade = highest_unused_msn_for_upgrade,
             .max_msn_in_ft = max_msn_in_ft,
             .time_of_last_optimize_begin = time_of_last_optimize_begin,
diff --git a/ft/ft-test-helpers.cc b/ft/ft-test-helpers.cc
index 2fafe8feeec..1468542a8d6 100644
--- a/ft/ft-test-helpers.cc
+++ b/ft/ft-test-helpers.cc
@@ -142,7 +142,6 @@ int toku_testsetup_leaf(FT_HANDLE brt, BLOCKNUM *blocknum, int n_children, char
 int toku_testsetup_nonleaf (FT_HANDLE brt, int height, BLOCKNUM *blocknum, int n_children, BLOCKNUM *children, char **keys, int *keylens) {
     FTNODE node;
     assert(testsetup_initialized);
-    assert(n_children<=FT_FANOUT);
     toku_create_new_ftnode(brt, &node, height, n_children);
     int i;
     for (i=0; i<n_children; i++) {
diff --git a/ft/ft.cc b/ft/ft.cc
index 4109b9b47b1..48a6912a74f 100644
--- a/ft/ft.cc
+++ b/ft/ft.cc
@@ -431,6 +431,7 @@ ft_header_create(FT_OPTIONS options, BLOCKNUM root_blocknum, TXNID root_xid_that
         .nodesize = options->nodesize,
         .basementnodesize = options->basementnodesize,
         .compression_method = options->compression_method,
+        .fanout = options->fanout,
         .highest_unused_msn_for_upgrade = { .msn = (MIN_MSN.msn - 1) },
         .max_msn_in_ft = ZERO_MSN,
         .time_of_last_optimize_begin = 0,
@@ -606,13 +607,16 @@ toku_ft_init(FT ft,
              TXNID root_xid_that_created,
              uint32_t target_nodesize,
              uint32_t target_basementnodesize,
-             enum toku_compression_method compression_method)
+             enum toku_compression_method compression_method,
+             uint32_t fanout
+             )
 {
     memset(ft, 0, sizeof *ft);
     struct ft_options options = {
         .nodesize = target_nodesize,
         .basementnodesize = target_basementnodesize,
         .compression_method = compression_method,
+        .fanout = fanout,
         .flags = 0,
         .compare_fun = NULL,
         .update_fun = NULL
@@ -633,6 +637,7 @@ ft_handle_open_for_redirect(FT_HANDLE *new_ftp, const char *fname_in_env, TOKUTX
     toku_ft_handle_set_nodesize(t, old_h->h->nodesize);
     toku_ft_handle_set_basementnodesize(t, old_h->h->basementnodesize);
     toku_ft_handle_set_compression_method(t, old_h->h->compression_method);
+    toku_ft_handle_set_fanout(t, old_h->h->fanout);
     CACHETABLE ct = toku_cachefile_get_cachetable(old_h->cf);
     int r = toku_ft_handle_open_with_dict_id(t, fname_in_env, 0, 0, ct, txn, old_h->dict_id);
     if (r != 0) {
@@ -1022,6 +1027,19 @@ void toku_ft_get_compression_method(FT ft, enum toku_compression_method *methodp
     toku_ft_unlock(ft);
 }
 
+void toku_ft_set_fanout(FT ft, unsigned int fanout) {
+    toku_ft_lock(ft);
+    ft->h->fanout = fanout;
+    ft->h->dirty = 1;
+    toku_ft_unlock(ft);
+}
+
+void toku_ft_get_fanout(FT ft, unsigned int *fanout) {
+    toku_ft_lock(ft);
+    *fanout = ft->h->fanout;
+    toku_ft_unlock(ft);
+}
+
 // mark the ft as a blackhole. any message injections will be a no op.
 void toku_ft_set_blackhole(FT_HANDLE ft_handle) {
     ft_handle->ft->blackhole = true;
diff --git a/ft/ft.h b/ft/ft.h
index 748c38aa138..92d1ba0b5ea 100644
--- a/ft/ft.h
+++ b/ft/ft.h
@@ -130,13 +130,14 @@ void toku_ft_note_hot_complete(FT_HANDLE brt, bool success, MSN msn_at_start_of_
 
 void
 toku_ft_init(
-    FT h,
+    FT ft,
     BLOCKNUM root_blocknum_on_disk,
     LSN checkpoint_lsn,
     TXNID root_xid_that_created,
     uint32_t target_nodesize,
     uint32_t target_basementnodesize,
-    enum toku_compression_method compression_method
+    enum toku_compression_method compression_method,
+    uint32_t fanout
     );
 
 int toku_dictionary_redirect_abort(FT old_h, FT new_h, TOKUTXN txn) __attribute__ ((warn_unused_result));
@@ -186,6 +187,8 @@ void toku_ft_set_basementnodesize(FT ft, unsigned int basementnodesize);
 void toku_ft_get_basementnodesize(FT ft, unsigned int *basementnodesize);
 void toku_ft_set_compression_method(FT ft, enum toku_compression_method method);
 void toku_ft_get_compression_method(FT ft, enum toku_compression_method *methodp);
+void toku_ft_set_fanout(FT ft, unsigned int fanout);
+void toku_ft_get_fanout(FT ft, unsigned int *fanout);
 void toku_node_save_ct_pair(CACHEKEY UU(key), void *value_data, PAIR p);
 
 // mark the ft as a blackhole. any message injections will be a no op.
diff --git a/ft/ftloader-internal.h b/ft/ftloader-internal.h
index ef8f618f22e..b8d55001641 100644
--- a/ft/ftloader-internal.h
+++ b/ft/ftloader-internal.h
@@ -288,6 +288,7 @@ struct fractal_thread_args {
     uint32_t                 target_nodesize;
     uint32_t                 target_basementnodesize;
     enum toku_compression_method target_compression_method;
+    uint32_t                 target_fanout;
 };
 
 void toku_ft_loader_set_n_rows(FTLOADER bl, uint64_t n_rows);
@@ -319,7 +320,8 @@ int toku_loader_write_brt_from_q_in_C (FTLOADER                bl,
                                        int                      which_db,
                                        uint32_t                 target_nodesize,
                                        uint32_t                 target_basementnodesize,
-                                       enum toku_compression_method target_compression_method);
+                                       enum toku_compression_method target_compression_method,
+                                       uint32_t                 fanout);
 
 int ft_loader_mergesort_row_array (struct row rows[/*n*/], int n, int which_db, DB *dest_db, ft_compare_func, FTLOADER, struct rowset *);
 
diff --git a/ft/ftloader.cc b/ft/ftloader.cc
index 8a536d541b9..35c0ee34394 100644
--- a/ft/ftloader.cc
+++ b/ft/ftloader.cc
@@ -2405,7 +2405,8 @@ static int toku_loader_write_ft_from_q (FTLOADER bl,
                                          int which_db,
                                          uint32_t target_nodesize,
                                          uint32_t target_basementnodesize,
-                                         enum toku_compression_method target_compression_method)
+                                         enum toku_compression_method target_compression_method,
+                                         uint32_t target_fanout)
 // Effect: Consume a sequence of rowsets work from a queue, creating a fractal tree.  Closes fd.
 {
     // set the number of fractal tree writer threads so that we can partition memory in the merger
@@ -2434,7 +2435,7 @@ static int toku_loader_write_ft_from_q (FTLOADER bl,
 
     // TODO: (Zardosht/Yoni/Leif), do this code properly
     struct ft ft;
-    toku_ft_init(&ft, (BLOCKNUM){0}, bl->load_lsn, root_xid_that_created, target_nodesize, target_basementnodesize, target_compression_method);
+    toku_ft_init(&ft, (BLOCKNUM){0}, bl->load_lsn, root_xid_that_created, target_nodesize, target_basementnodesize, target_compression_method, target_fanout);
 
     struct dbout out;
     ZERO_STRUCT(out);
@@ -2680,18 +2681,19 @@ int toku_loader_write_brt_from_q_in_C (FTLOADER                bl,
                                        int                      which_db,
                                        uint32_t                 target_nodesize,
                                        uint32_t                 target_basementnodesize,
-                                       enum toku_compression_method target_compression_method)
+                                       enum toku_compression_method target_compression_method,
+                                       uint32_t                 target_fanout)
 // This is probably only for testing.
 {
     target_nodesize = target_nodesize == 0 ? default_loader_nodesize : target_nodesize;
     target_basementnodesize = target_basementnodesize == 0 ? default_loader_basementnodesize : target_basementnodesize;
-    return toku_loader_write_ft_from_q (bl, descriptor, fd, progress_allocation, q, total_disksize_estimate, which_db, target_nodesize, target_basementnodesize, target_compression_method);
+    return toku_loader_write_ft_from_q (bl, descriptor, fd, progress_allocation, q, total_disksize_estimate, which_db, target_nodesize, target_basementnodesize, target_compression_method, target_fanout);
 }
 
 
 static void* fractal_thread (void *ftav) {
     struct fractal_thread_args *fta = (struct fractal_thread_args *)ftav;
-    int r = toku_loader_write_ft_from_q (fta->bl, fta->descriptor, fta->fd, fta->progress_allocation, fta->q, fta->total_disksize_estimate, fta->which_db, fta->target_nodesize, fta->target_basementnodesize, fta->target_compression_method);
+    int r = toku_loader_write_ft_from_q (fta->bl, fta->descriptor, fta->fd, fta->progress_allocation, fta->q, fta->total_disksize_estimate, fta->which_db, fta->target_nodesize, fta->target_basementnodesize, fta->target_compression_method, fta->target_fanout);
     fta->errno_result = r;
     return NULL;
 }
@@ -2727,7 +2729,7 @@ static int loader_do_i (FTLOADER bl,
             r = get_error_errno(); goto error;
         }
 
-        uint32_t target_nodesize, target_basementnodesize;
+        uint32_t target_nodesize, target_basementnodesize, target_fanout;
         enum toku_compression_method target_compression_method;
         r = dest_db->get_pagesize(dest_db, &target_nodesize);
         invariant_zero(r);
@@ -2735,6 +2737,8 @@ static int loader_do_i (FTLOADER bl,
         invariant_zero(r);
         r = dest_db->get_compression_method(dest_db, &target_compression_method);
         invariant_zero(r);
+        r = dest_db->get_fanout(dest_db, &target_fanout);
+        invariant_zero(r);
 
         // This structure must stay live until the join below.
         struct fractal_thread_args fta = { bl,
@@ -2748,6 +2752,7 @@ static int loader_do_i (FTLOADER bl,
                                            target_nodesize,
                                            target_basementnodesize,
                                            target_compression_method,
+                                           target_fanout
         };
 
         r = toku_pthread_create(bl->fractal_threads+which_db, NULL, fractal_thread, (void*)&fta);
diff --git a/ft/tests/ft-bfe-query.cc b/ft/tests/ft-bfe-query.cc
index e5e8dcc8643..a545e458d94 100644
--- a/ft/tests/ft-bfe-query.cc
+++ b/ft/tests/ft-bfe-query.cc
@@ -420,7 +420,8 @@ test_prefetching(void) {
                  TXNID_NONE,
                  4*1024*1024,
                  128*1024,
-                 TOKU_DEFAULT_COMPRESSION_METHOD);
+                 TOKU_DEFAULT_COMPRESSION_METHOD,
+                 16);
     brt->ft = brt_h;
     toku_blocktable_create_new(&brt_h->blocktable);
     { int r_truncate = ftruncate(fd, 0); CKERR(r_truncate); }
diff --git a/ft/tests/ft-clock-test.cc b/ft/tests/ft-clock-test.cc
index 606832a5df6..aefb9b50183 100644
--- a/ft/tests/ft-clock-test.cc
+++ b/ft/tests/ft-clock-test.cc
@@ -355,7 +355,8 @@ test_serialize_nonleaf(void) {
                  TXNID_NONE,
                  4*1024*1024,
                  128*1024,
-                 TOKU_DEFAULT_COMPRESSION_METHOD);
+                 TOKU_DEFAULT_COMPRESSION_METHOD,
+                 16);
     brt->ft = brt_h;
     
     toku_blocktable_create_new(&brt_h->blocktable);
@@ -438,7 +439,8 @@ test_serialize_leaf(void) {
                  TXNID_NONE,
                  4*1024*1024,
                  128*1024,
-                 TOKU_DEFAULT_COMPRESSION_METHOD);
+                 TOKU_DEFAULT_COMPRESSION_METHOD,
+                 16);
     brt->ft = brt_h;
     
     toku_blocktable_create_new(&brt_h->blocktable);
diff --git a/ft/tests/ft-serialize-benchmark.cc b/ft/tests/ft-serialize-benchmark.cc
index a5cbc2f684e..42351e3108d 100644
--- a/ft/tests/ft-serialize-benchmark.cc
+++ b/ft/tests/ft-serialize-benchmark.cc
@@ -189,7 +189,8 @@ test_serialize_leaf(int valsize, int nelts, double entropy) {
                  TXNID_NONE,
                  4*1024*1024,
                  128*1024,
-                 TOKU_DEFAULT_COMPRESSION_METHOD);
+                 TOKU_DEFAULT_COMPRESSION_METHOD,
+                 16);
     brt->ft = brt_h;
     
     brt_h->compare_fun = long_key_cmp;
@@ -319,7 +320,8 @@ test_serialize_nonleaf(int valsize, int nelts, double entropy) {
                  TXNID_NONE,
                  4*1024*1024,
                  128*1024,
-                 TOKU_DEFAULT_COMPRESSION_METHOD);
+                 TOKU_DEFAULT_COMPRESSION_METHOD,
+                 16);
     brt->ft = brt_h;
     
     brt_h->compare_fun = long_key_cmp;
diff --git a/ft/tests/ft-serialize-test.cc b/ft/tests/ft-serialize-test.cc
index 774948ddf95..482cd5bb336 100644
--- a/ft/tests/ft-serialize-test.cc
+++ b/ft/tests/ft-serialize-test.cc
@@ -306,7 +306,8 @@ test_serialize_leaf_check_msn(enum ftnode_verify_type bft, bool do_clone) {
                  TXNID_NONE,
                  4*1024*1024,
                  128*1024,
-                 TOKU_DEFAULT_COMPRESSION_METHOD);
+                 TOKU_DEFAULT_COMPRESSION_METHOD,
+                 16);
     brt->ft = brt_h;
     toku_blocktable_create_new(&brt_h->blocktable);
     { int r_truncate = ftruncate(fd, 0); CKERR(r_truncate); }
@@ -449,7 +450,8 @@ test_serialize_leaf_with_large_pivots(enum ftnode_verify_type bft, bool do_clone
                  TXNID_NONE,
                  4*1024*1024,
                  128*1024,
-                 TOKU_DEFAULT_COMPRESSION_METHOD);
+                 TOKU_DEFAULT_COMPRESSION_METHOD,
+                 16);
     brt->ft = brt_h;
     toku_blocktable_create_new(&brt_h->blocktable);
     { int r_truncate = ftruncate(fd, 0); CKERR(r_truncate); }
@@ -586,7 +588,8 @@ test_serialize_leaf_with_many_rows(enum ftnode_verify_type bft, bool do_clone) {
                  TXNID_NONE,
                  4*1024*1024,
                  128*1024,
-                 TOKU_DEFAULT_COMPRESSION_METHOD);
+                 TOKU_DEFAULT_COMPRESSION_METHOD,
+                 16);
     brt->ft = brt_h;
     
     toku_blocktable_create_new(&brt_h->blocktable);
@@ -733,7 +736,8 @@ test_serialize_leaf_with_large_rows(enum ftnode_verify_type bft, bool do_clone)
                  TXNID_NONE,
                  4*1024*1024,
                  128*1024,
-                 TOKU_DEFAULT_COMPRESSION_METHOD);
+                 TOKU_DEFAULT_COMPRESSION_METHOD,
+                 16);
     brt->ft = brt_h;
     
     toku_blocktable_create_new(&brt_h->blocktable);
@@ -881,7 +885,8 @@ test_serialize_leaf_with_empty_basement_nodes(enum ftnode_verify_type bft, bool
                  TXNID_NONE,
                  4*1024*1024,
                  128*1024,
-                 TOKU_DEFAULT_COMPRESSION_METHOD);
+                 TOKU_DEFAULT_COMPRESSION_METHOD,
+                 16);
     brt->ft = brt_h;
     
     toku_blocktable_create_new(&brt_h->blocktable);
@@ -1009,7 +1014,8 @@ test_serialize_leaf_with_multiple_empty_basement_nodes(enum ftnode_verify_type b
                  TXNID_NONE,
                  4*1024*1024,
                  128*1024,
-                 TOKU_DEFAULT_COMPRESSION_METHOD);
+                 TOKU_DEFAULT_COMPRESSION_METHOD,
+                 16);
     brt->ft = brt_h;
     
     toku_blocktable_create_new(&brt_h->blocktable);
@@ -1134,7 +1140,8 @@ test_serialize_nonleaf(enum ftnode_verify_type bft, bool do_clone) {
                  TXNID_NONE,
                  4*1024*1024,
                  128*1024,
-                 TOKU_DEFAULT_COMPRESSION_METHOD);
+                 TOKU_DEFAULT_COMPRESSION_METHOD,
+                 16);
     brt->ft = brt_h;
     
     toku_blocktable_create_new(&brt_h->blocktable);
diff --git a/ft/tests/ftloader-test-writer-errors.cc b/ft/tests/ftloader-test-writer-errors.cc
index 5f0728cc02c..c72b6f847a3 100644
--- a/ft/tests/ftloader-test-writer-errors.cc
+++ b/ft/tests/ftloader-test-writer-errors.cc
@@ -213,7 +213,7 @@ static int write_dbfile (char *tf_template, int n, char *output_name, bool expec
     ft_loader_set_error_function(&bl.error_callback, NULL, NULL);
     ft_loader_set_poll_function(&bl.poll_callback, loader_poll_callback, NULL);
 
-    result = toku_loader_write_brt_from_q_in_C(&bl, &desc, fd, 1000, q2, size_est, 0, 0, 0, TOKU_DEFAULT_COMPRESSION_METHOD);
+    result = toku_loader_write_brt_from_q_in_C(&bl, &desc, fd, 1000, q2, size_est, 0, 0, 0, TOKU_DEFAULT_COMPRESSION_METHOD, 16);
 
     toku_set_func_malloc_only(NULL);
     toku_set_func_realloc_only(NULL);
diff --git a/ft/tests/ftloader-test-writer.cc b/ft/tests/ftloader-test-writer.cc
index 67bb47a7c5e..53d6bde27a0 100644
--- a/ft/tests/ftloader-test-writer.cc
+++ b/ft/tests/ftloader-test-writer.cc
@@ -262,7 +262,7 @@ static void test_write_dbfile (char *tf_template, int n, char *output_name, TXNI
     assert(fd>=0);
 
     if (verbose) traceit("write to file");
-    r = toku_loader_write_brt_from_q_in_C(&bl, &desc, fd, 1000, q2, size_est, 0, 0, 0, TOKU_DEFAULT_COMPRESSION_METHOD);
+    r = toku_loader_write_brt_from_q_in_C(&bl, &desc, fd, 1000, q2, size_est, 0, 0, 0, TOKU_DEFAULT_COMPRESSION_METHOD, 16);
     assert(r==0);
 
     r = queue_destroy(q2);
diff --git a/ft/tests/ftloader-test.cc b/ft/tests/ftloader-test.cc
index 4b7a3139adb..2fc2d309f64 100644
--- a/ft/tests/ftloader-test.cc
+++ b/ft/tests/ftloader-test.cc
@@ -425,7 +425,7 @@ static void test_merge_files (const char *tf_template, const char *output_name)
     int fd = open(output_name, O_RDWR | O_CREAT | O_BINARY, S_IRWXU|S_IRWXG|S_IRWXO);
     assert(fd>=0);
     
-    r = toku_loader_write_brt_from_q_in_C(&bl, &desc, fd, 1000, q, size_est, 0, 0, 0, TOKU_DEFAULT_COMPRESSION_METHOD);
+    r = toku_loader_write_brt_from_q_in_C(&bl, &desc, fd, 1000, q, size_est, 0, 0, 0, TOKU_DEFAULT_COMPRESSION_METHOD, 16);
     assert(r==0);
 
     destroy_merge_fileset(&fs);
diff --git a/ft/tests/test-inc-split.cc b/ft/tests/test-inc-split.cc
index 6d0a6349b5c..cafcb496f7a 100644
--- a/ft/tests/test-inc-split.cc
+++ b/ft/tests/test-inc-split.cc
@@ -130,10 +130,10 @@ const char *fname = TOKU_TEST_FILENAME;
 
 static void
 doit (int ksize __attribute__((__unused__))) {
-    BLOCKNUM cnodes[FT_FANOUT], bnode, anode;
+    BLOCKNUM cnodes[16], bnode, anode;
 
-    char *keys[FT_FANOUT-1];
-    int keylens[FT_FANOUT-1];
+    char *keys[16-1];
+    int keylens[16-1];
     int i;
     int r;
     
@@ -144,7 +144,7 @@ doit (int ksize __attribute__((__unused__))) {
 
     toku_testsetup_initialize();  // must precede any other toku_testsetup calls
 
-    for (i=0; i<FT_FANOUT; i++) {
+    for (i=0; i<16; i++) {
 	r=toku_testsetup_leaf(t, &cnodes[i], 1, NULL, NULL);
 	assert(r==0);
 	char key[KSIZE+10];
@@ -156,16 +156,16 @@ doit (int ksize __attribute__((__unused__))) {
     }
 
     // Now we have a bunch of leaves, all of which are with 100 bytes of full.
-    for (i=0; i+1<FT_FANOUT; i++) {
+    for (i=0; i+1<16; i++) {
 	char key[TOKU_PSIZE];
 	keylens[i]=1+snprintf(key, TOKU_PSIZE, "%08d", (i+1)*10000);
 	keys[i]=toku_strdup(key);
     }
 
-    r = toku_testsetup_nonleaf(t, 1, &bnode, FT_FANOUT, cnodes, keys, keylens);
+    r = toku_testsetup_nonleaf(t, 1, &bnode, 16, cnodes, keys, keylens);
     assert(r==0);
 
-    for (i=0; i+1<FT_FANOUT; i++) {
+    for (i=0; i+1<16; i++) {
 	toku_free(keys[i]);
     }
 
diff --git a/src/ydb_db.cc b/src/ydb_db.cc
index 3fde19f6bdc..e696deb3b30 100644
--- a/src/ydb_db.cc
+++ b/src/ydb_db.cc
@@ -688,6 +688,29 @@ toku_db_get_compression_method(DB *db, enum toku_compression_method *compression
     return 0;
 }
 
+static int 
+toku_db_change_fanout(DB *db, unsigned int fanout) {
+    HANDLE_PANICKED_DB(db);
+    if (!db_opened(db)) return EINVAL;
+    toku_ft_handle_set_fanout(db->i->ft_handle, fanout);
+    return 0;
+}
+
+static int 
+toku_db_set_fanout(DB *db, unsigned int fanout) {
+    HANDLE_PANICKED_DB(db);
+    if (db_opened(db)) return EINVAL;
+    toku_ft_handle_set_fanout(db->i->ft_handle, fanout);
+    return 0;
+}
+
+static int 
+toku_db_get_fanout(DB *db, unsigned int *fanout) {
+    HANDLE_PANICKED_DB(db);
+    toku_ft_handle_get_fanout(db->i->ft_handle, fanout);
+    return 0;
+}
+
 static int
 toku_db_get_fractal_tree_info64(DB *db, uint64_t *num_blocks_allocated, uint64_t *num_blocks_in_use, uint64_t *size_allocated, uint64_t *size_in_use) {
     HANDLE_PANICKED_DB(db);
@@ -1034,6 +1057,9 @@ toku_db_create(DB ** db, DB_ENV * env, uint32_t flags) {
     USDB(set_compression_method);
     USDB(get_compression_method);
     USDB(change_compression_method);
+    USDB(set_fanout);
+    USDB(get_fanout);
+    USDB(change_fanout);
     USDB(set_flags);
     USDB(get_flags);
     USDB(fd);