diff --git a/src/lib_shell/state.ml b/src/lib_shell/state.ml
index d5e504187..34bbee60c 100644
--- a/src/lib_shell/state.ml
+++ b/src/lib_shell/state.ml
@@ -889,11 +889,15 @@ let may_create_chain state chain genesis =
 
 let read
     ?patch_context
+    ?(store_mapsize=4_096_000_000_000L)
+    ?(context_mapsize=40_960_000_000L)
     ~store_root
     ~context_root
     genesis =
-  Store.init store_root >>=? fun global_store ->
-  Context.init ?patch_context ~root:context_root >>= fun context_index ->
+  Store.init ~mapsize:store_mapsize store_root >>=? fun global_store ->
+  Context.init
+    ~mapsize:context_mapsize ?patch_context
+    context_root >>= fun context_index ->
   let global_data = {
     chains = Chain_id.Table.create 17 ;
     global_store ;
diff --git a/src/lib_shell/state.mli b/src/lib_shell/state.mli
index e6e2511e8..ae115dde0 100644
--- a/src/lib_shell/state.mli
+++ b/src/lib_shell/state.mli
@@ -233,6 +233,8 @@ end
     the databases. *)
 val read:
   ?patch_context:(Context.t -> Context.t Lwt.t) ->
+  ?store_mapsize:int64 ->
+  ?context_mapsize:int64 ->
   store_root:string ->
   context_root:string ->
   Chain.genesis ->
diff --git a/src/lib_shell/store.ml b/src/lib_shell/store.ml
index 0ac424dc5..692922cf7 100644
--- a/src/lib_shell/store.ml
+++ b/src/lib_shell/store.ml
@@ -261,8 +261,8 @@ module Protocol = struct
 
 end
 
-let init dir =
-  Raw_store.init dir >>=? fun s ->
+let init ?mapsize dir =
+  Raw_store.init ?mapsize dir >>=? fun s ->
   Block.register s ;
   Protocol.register s ;
   return s
diff --git a/src/lib_shell/store.mli b/src/lib_shell/store.mli
index e09388aa6..fbd6a3a29 100644
--- a/src/lib_shell/store.mli
+++ b/src/lib_shell/store.mli
@@ -12,8 +12,9 @@ open Store_sigs
 type t
 type global_store = t
 
-(** Open or initialize a store at a given path. *)
-val init: string -> t tzresult Lwt.t
+(** [init ~mapsize path] returns an initialized store at [path] of
+    maximum capacity [mapsize] bytes. *)
+val init: ?mapsize:int64 -> string -> t tzresult Lwt.t
 val close : t -> unit
 
 
diff --git a/src/lib_shell/test/assert.ml b/src/lib_shell/test/assert.ml
index 700576882..4289e1658 100644
--- a/src/lib_shell/test/assert.ml
+++ b/src/lib_shell/test/assert.ml
@@ -10,7 +10,9 @@
 let fail expected given msg =
   Format.kasprintf Pervasives.failwith
     "@[%s@ expected: %s@ got: %s@]" msg expected given
-let fail_msg fmt = Format.kasprintf (fail "" "") fmt
+
+let fail_msg ?(expected="") ?(given="") fmt =
+  Format.kasprintf (fail expected given) fmt
 
 let default_printer _ = ""
 
@@ -47,11 +49,12 @@ let make_equal_list eq prn ?(msg="") x y =
         if eq hd_x hd_y then
           iter (succ i) tl_x tl_y
         else
-          let fm = Printf.sprintf "%s (at index %d)" msg i in
-          fail (prn hd_x) (prn hd_y) fm
+          fail_msg ~expected:(prn hd_x) ~given:(prn hd_y)
+            "%s (at index %d)" msg i
     | _ :: _, [] | [], _ :: _ ->
-        let fm = Printf.sprintf "%s (lists of different sizes)" msg in
-        fail_msg "%s" fm
+        fail_msg ~expected:"" ~given:""
+          "%s (lists of different sizes %d %d)" msg
+          (List.length x) (List.length y)
     | [], [] ->
         () in
   iter 0 x y
diff --git a/src/lib_shell/test/test_state.ml b/src/lib_shell/test/test_state.ml
index 195ec1e33..26920bc10 100644
--- a/src/lib_shell/test/test_state.ml
+++ b/src/lib_shell/test/test_state.ml
@@ -152,6 +152,8 @@ let wrap_state_init f base_dir =
     let store_root = base_dir // "store" in
     let context_root = base_dir // "context" in
     State.read
+      ~store_mapsize:4_096_000_000L
+      ~context_mapsize:4_096_000_000L
       ~store_root
       ~context_root
       genesis >>=? fun (state, chain) ->
diff --git a/src/lib_shell/test/test_store.ml b/src/lib_shell/test/test_store.ml
index 1023f9685..65f9f826b 100644
--- a/src/lib_shell/test/test_store.ml
+++ b/src/lib_shell/test/test_store.ml
@@ -28,13 +28,16 @@ let genesis_time =
 
 (** *)
 
+let mapsize = 4_096_000_000L (* ~4 GiB *)
+
 let wrap_store_init f _ () =
   Lwt_utils_unix.with_tempdir "tezos_test_" begin fun base_dir ->
     let root = base_dir // "store" in
-    Store.init root >>= function
+    Store.init ~mapsize root >>= function
     | Ok store ->
-        f store >>= fun () ->
-        Lwt.return ()
+        Lwt.finalize
+          (fun () -> f store)
+          (fun () -> Store.close store ; Lwt.return_unit)
     | Error err ->
         Format.kasprintf Pervasives.failwith
           "@[Cannot initialize store:@ %a@]" pp_print_error err
@@ -43,10 +46,11 @@ let wrap_store_init f _ () =
 let wrap_raw_store_init f _ () =
   Lwt_utils_unix.with_tempdir "tezos_test_" begin fun base_dir ->
     let root = base_dir // "store" in
-    Raw_store.init root >>= function
+    Raw_store.init ~mapsize root >>= function
     | Ok store ->
-        f store >>= fun () ->
-        Lwt.return ()
+        Lwt.finalize
+          (fun () -> f store)
+          (fun () -> Raw_store.close store ; Lwt.return_unit)
     | Error err ->
         Format.kasprintf Pervasives.failwith
           "@[Cannot initialize store:@ %a@]" pp_print_error err
@@ -153,11 +157,15 @@ let test_expand s =
 
 let check (type t)
     (module Store: Store_sigs.STORE with type t = t) (s: Store.t) k d =
-  Store.read_opt s k >|= fun d' ->
-  if d' <> Some d then begin
-    Assert.fail_msg
-      "Error while reading key %S\n%!"  (String.concat Filename.dir_sep k) ;
-  end
+  Store.read_opt s k >|= function
+  | Some d' when MBytes.equal d d' -> ()
+  | Some d' ->
+      Assert.fail_msg ~expected:(MBytes.to_string d) ~given:(MBytes.to_string d')
+        "Error while reading key %d %S\n%!"
+        Cstruct.(compare (of_bigarray d) (of_bigarray d')) (String.concat Filename.dir_sep k)
+  | None ->
+      Assert.fail_msg ~expected:(MBytes.to_string d) ~given:""
+        "Error while reading key %S\n%!" (String.concat Filename.dir_sep k)
 
 let check_none (type t)
     (module Store: Store_sigs.STORE with type t = t) (s: Store.t) k =
@@ -179,7 +187,7 @@ let test_generic (type t)
 
 let list (type t)
     (module Store: Store_sigs.STORE with type t = t) (s: Store.t) k =
-  Store.fold_keys s k ~init:[] ~f:(fun k acc -> Lwt.return (k :: acc))
+  Store.keys s k
 
 let test_generic_list (type t)
     (module Store: Store_sigs.STORE with type t = t) (s: Store.t) =
@@ -216,12 +224,11 @@ let test_hashset (type t)
       (Make_substore(Store)(struct let name = ["test_set"] end))
       (Block_hash)
       (BlockSet) in
-  let bhset : BlockSet.t = BlockSet.add bh2 (BlockSet.add bh1 BlockSet.empty) in
+  let bhset = BlockSet.(add bh2 (add bh1 empty)) in
   StoreSet.store_all s bhset >>= fun () ->
   StoreSet.read_all s >>= fun bhset' ->
   Assert.equal_block_set ~msg:__LOC__ bhset bhset' ;
-  let bhset2 =
-    Pervasives.(bhset |> BlockSet.add bh3 |> BlockSet.remove bh1) in
+  let bhset2 = BlockSet.(bhset |> add bh3 |> remove bh1) in
   StoreSet.store_all s bhset2 >>= fun () ->
   StoreSet.read_all s >>= fun bhset2' ->
   Assert.equal_block_set ~msg:__LOC__ bhset2 bhset2' ;
@@ -252,14 +259,11 @@ let test_hashmap (type t)
        end))
       (BlockMap) in
   let eq = (=) in
-  let map =
-    Pervasives.(BlockMap.empty |>
-                BlockMap.add bh1 (1, 'a') |> BlockMap.add bh2 (2, 'b')) in
+  let map = BlockMap.(empty |> add bh1 (1, 'a') |> add bh2 (2, 'b')) in
   StoreMap.store_all s map >>= fun () ->
   StoreMap.read_all s >>= fun map' ->
   Assert.equal_block_map ~msg:__LOC__ ~eq map map' ;
-  let map2 =
-    Pervasives.(map |> BlockMap.add bh3 (3, 'c') |> BlockMap.remove bh1) in
+  let map2 = map |> BlockMap.add bh3 (3, 'c') |> BlockMap.remove bh1 in
   StoreMap.store_all s map2 >>= fun () ->
   StoreMap.read_all s >>= fun map2' ->
   Assert.equal_block_map ~msg:__LOC__ ~eq map2 map2' ;
@@ -324,16 +328,10 @@ let test_subblock s =
   SubBlocksSet.known s bh2 >>= fun known ->
   Assert.is_true ~msg:__LOC__ known ;
   SubBlocksSet.read_all s >>= fun set ->
-  let set' =
-    Block_hash.Set.empty
-    |> Block_hash.Set.add bh1
-    |> Block_hash.Set.add bh2 in
+  let set' = Block_hash.Set.(empty |> add bh1 |> add bh2) in
   Assert.equal_block_set ~msg:__LOC__ set set' ;
   SubBlocksSet.remove s bh2 >>= fun () ->
-  let set =
-    Block_hash.Set.empty
-    |> Block_hash.Set.add bh3'
-    |> Block_hash.Set.add bh3 in
+  let set = Block_hash.Set.(empty |> add bh3' |> add bh3) in
   SubBlocksSet.store_all s set >>= fun () ->
   SubBlocksSet.elements s >>= fun elts ->
   Assert.equal_block_hash_list ~msg:__LOC__
@@ -355,10 +353,7 @@ let test_subblock s =
   SubBlocksMap.read_opt s bh1 >>= fun v1' ->
   Assert.equal ~msg:__LOC__ (Some v1) v1' ;
   Assert.is_true ~msg:__LOC__ known ;
-  let map =
-    Block_hash.Map.empty
-    |> Block_hash.Map.add bh1 v1
-    |> Block_hash.Map.add bh2 v2 in
+  let map = Block_hash.Map.(empty |> add bh1 v1 |> add bh2 v2) in
   SubBlocksMap.read_all s >>= fun map' ->
   Assert.equal_block_map ~eq:(=) ~msg:__LOC__ map map' ;
 
diff --git a/src/lib_storage/context.ml b/src/lib_storage/context.ml
index a053a71f2..a79080668 100644
--- a/src/lib_storage/context.ml
+++ b/src/lib_storage/context.ml
@@ -66,7 +66,7 @@ module IrminBlake2B : Irmin.Hash.S with type t = Context_hash.t = struct
 end
 
 module GitStore =
-  Irmin_leveldb.Make
+  Irmin_lmdb.Make
     (Metadata)
     (MBytesContent)
     (Irmin.Path.String_list)
@@ -202,9 +202,9 @@ let fork_test_chain v ~protocol ~expiration =
 
 (*-- Initialisation ----------------------------------------------------------*)
 
-let init ?patch_context ~root =
+let init ?patch_context ?mapsize root =
   GitStore.Repo.v
-    (Irmin_leveldb.config root) >>= fun repo ->
+    (Irmin_lmdb.config ?mapsize root) >>= fun repo ->
   Lwt.return {
     path = root ;
     repo ;
diff --git a/src/lib_storage/context.mli b/src/lib_storage/context.mli
index 2cad47acb..0ef58eb6e 100644
--- a/src/lib_storage/context.mli
+++ b/src/lib_storage/context.mli
@@ -19,7 +19,8 @@ type context = t
 (** Open or initialize a versioned store at a given path. *)
 val init:
   ?patch_context:(context -> context Lwt.t) ->
-  root:string ->
+  ?mapsize:int64 ->
+  string ->
   index Lwt.t
 
 val commit_genesis:
diff --git a/src/lib_storage/jbuild b/src/lib_storage/jbuild
index 2963d41cc..757e2ee25 100644
--- a/src/lib_storage/jbuild
+++ b/src/lib_storage/jbuild
@@ -4,8 +4,8 @@
  ((name tezos_storage)
   (public_name tezos-storage)
   (libraries (tezos-base
-              leveldb
-              irmin-leveldb))
+              lmdb
+              irmin-lmdb))
   (flags (:standard -w -9+27-30-32-40@8
                     -safe-string
                     -open Tezos_base__TzPervasives))))
diff --git a/src/lib_storage/raw_store.ml b/src/lib_storage/raw_store.ml
index 0a8b7bce9..fd66ed7b6 100644
--- a/src/lib_storage/raw_store.ml
+++ b/src/lib_storage/raw_store.ml
@@ -7,9 +7,13 @@
 (*                                                                        *)
 (**************************************************************************)
 
-module List = ListLabels
+open Rresult
+
+type t = {
+  dir : Lmdb.t ;
+  parent : (Lmdb.rw Lmdb.txn * Lmdb.db * Lmdb.rw Lmdb.cursor) Lwt.key ;
+}
 
-type t = LevelDB.db
 type key = string list
 type value = MBytes.t
 
@@ -32,60 +36,128 @@ let () =
 let concat = String.concat "/"
 let split = String.split_on_char '/'
 
-let init path =
-  try
-    return (LevelDB.open_db path)
-  with exn ->
-    Lwt.return (error_exn exn)
+let lwt_fail_error err =
+  Lwt.fail_with (Lmdb.string_of_error err)
 
-let close t = LevelDB.close t
+let of_result = function
+  | Ok res -> Lwt.return res
+  | Error err -> lwt_fail_error err
 
-let known t key =
-  Lwt.return (LevelDB.mem t (concat key))
+let (>>=?) v f =
+  match v with
+  | Error err -> lwt_fail_error err
+  | Ok v -> f v
 
-let read_opt t key =
-  Lwt.return (Option.map ~f:MBytes.of_string (LevelDB.get t (concat key)))
+let init ?mapsize path =
+  if not (Sys.file_exists path) then Unix.mkdir path 0o755 ;
+  match Lmdb.opendir ?mapsize ~flags:[NoTLS] path 0o644 with
+  | Ok dir -> return { dir ; parent = Lwt.new_key () }
+  | Error err -> failwith "%a" Lmdb.pp_error err
 
-let read t key =
-  match LevelDB.get t (concat key) with
-  | None -> fail (Unknown key)
-  | Some k -> return (MBytes.of_string k)
+let close { dir } = Lmdb.closedir dir
 
-let read_exn t key =
-  Lwt.wrap2 LevelDB.get_exn t (concat key) >|= MBytes.of_string
+let known { dir ; parent } key =
+  begin match Lwt.get parent with
+    | Some (txn, db, _cursor) -> Lmdb.mem txn db (concat key)
+    | None ->
+        Lmdb.with_ro_db dir ~f:begin fun txn db ->
+          Lmdb.mem txn db (concat key)
+        end
+  end |> of_result
 
-let store t k v =
-  LevelDB.put t (concat k) (MBytes.to_string v) ;
-  Lwt.return_unit
+let read_opt { dir ; parent } key =
+  begin match Lwt.get parent with
+    | Some (txn, db, _cursor) -> Lmdb.get txn db (concat key) >>| MBytes.copy
+    | None ->
+        Lmdb.with_ro_db dir ~f:begin fun txn db ->
+          Lmdb.get txn db (concat key) >>| MBytes.copy
+        end
+  end |> function
+  | Ok v -> Lwt.return_some v
+  | Error KeyNotFound -> Lwt.return_none
+  | Error err -> lwt_fail_error err
 
-let remove t k =
-  LevelDB.delete t (concat k) ;
-  Lwt.return_unit
+let read { dir ; parent } key =
+  begin match Lwt.get parent with
+    | Some (txn, db, _cursor) -> Lmdb.get txn db (concat key) >>| MBytes.copy
+    | None ->
+        Lmdb.with_ro_db dir ~f:begin fun txn db ->
+          Lmdb.get txn db (concat key) >>| MBytes.copy
+        end
+  end |> function
+  | Ok v -> return v
+  | Error _err -> fail (Unknown key)
+
+let read_exn { dir ; parent } key =
+  begin match Lwt.get parent with
+    | Some (txn, db, _cursor) -> Lmdb.get txn db (concat key) >>| MBytes.copy
+    | None ->
+        Lmdb.with_ro_db dir ~f:begin fun txn db ->
+          Lmdb.get txn db (concat key) >>| MBytes.copy
+        end
+  end |> of_result
+
+let store { dir ; parent } k v =
+  begin match Lwt.get parent with
+    | Some (txn, db, _cursor) -> Lmdb.put txn db (concat k) v
+    | None ->
+        Lmdb.with_rw_db dir ~f:begin fun txn db ->
+          Lmdb.put txn db (concat k) v
+        end
+  end |> of_result
+
+let remove { dir ; parent } k =
+  let remove txn db =
+    match Lmdb.del txn db (concat k) with
+    | Ok () -> Ok ()
+    | Error KeyNotFound -> Ok ()
+    | Error err -> Error err in
+  begin match Lwt.get parent with
+    | Some (txn, db, _cursor) -> remove txn db
+    | None -> Lmdb.with_rw_db dir ~f:remove
+  end |> of_result
 
 let is_prefix s s' =
   String.(length s <= length s' && compare s (sub s' 0 (length s)) = 0)
 
-let known_dir t k =
-  let ret = ref false in
+let known_dir { dir ; parent } k =
   let k = concat k in
-  LevelDB.iter_from begin fun kk _ ->
-    if is_prefix k kk then ret := true ;
-    false
-  end t k ;
-  Lwt.return !ret
+  let cursor_fun cursor =
+    Lmdb.cursor_at cursor k >>= fun () ->
+    Lmdb.cursor_get cursor >>| fun (first_k, _v) ->
+    (is_prefix k (MBytes.to_string first_k))
+  in
+  begin match Lwt.get parent with
+    | Some (txn, db, _cursor) ->
+        Lmdb.with_cursor txn db ~f:cursor_fun
+    | None ->
+        Lmdb.with_ro_db dir ~f:begin fun txn db ->
+          Lmdb.with_cursor txn db ~f:cursor_fun
+        end
+  end |> of_result
 
-let remove_dir t k =
+let remove_dir { dir ; parent } k =
   let k = concat k in
-  let batch = LevelDB.Batch.make () in
-  LevelDB.iter_from begin fun kk _ ->
-    if is_prefix k kk then begin
-      LevelDB.Batch.delete batch kk ;
-      true
-    end
-    else false
-  end t k ;
-  LevelDB.Batch.write t batch ;
-  Lwt.return_unit
+  let cursor_fun cursor =
+    Lmdb.cursor_at cursor k >>= fun () ->
+    Lmdb.cursor_iter cursor ~f:begin fun (kk, _v) ->
+      let kk_string = MBytes.to_string kk in
+      if is_prefix k kk_string then begin
+        Lmdb.cursor_del cursor
+      end
+      else Error KeyNotFound
+    end in
+  begin match Lwt.get parent with
+    | Some (txn, db, _cursor) ->
+        Lmdb.with_cursor txn db ~f:cursor_fun
+    | None ->
+        Lmdb.with_rw_db dir ~f:begin fun txn db ->
+          Lmdb.with_cursor txn db ~f:cursor_fun
+        end
+  end |> function
+  | Error KeyNotFound
+  | Ok () -> Lwt.return_unit
+  | Error err -> lwt_fail_error err
 
 let list_equal l1 l2 len =
   if len < 0 || len > List.length l1 || len > List.length l2
@@ -116,45 +188,81 @@ let list_sub l pos len =
         else inner (h :: acc, pred n) t in
   inner ([], len) l
 
+let with_rw_cursor_lwt ?sync ?metasync ?flags ?name { dir ; parent } ~f =
+  let local_parent =
+    match Lwt.get parent with
+    | None -> None
+    | Some (txn, _db, _cursor) -> Some txn in
+  Lmdb.create_rw_txn
+    ?sync ?metasync ?parent:local_parent dir >>=? fun txn ->
+  Lmdb.opendb ?flags ?name txn >>=? fun db ->
+  Lmdb.opencursor txn db >>=? fun cursor ->
+  Lwt.with_value parent (Some (txn, db, cursor)) begin fun () ->
+    Lwt.try_bind (fun () -> f cursor)
+      begin fun res ->
+        Lmdb.cursor_close cursor ;
+        Lmdb.commit_txn txn >>=? fun () ->
+        Lwt.return res
+      end
+      begin fun exn ->
+        Lmdb.cursor_close cursor ;
+        Lmdb.abort_txn txn ;
+        Lwt.fail exn
+      end
+  end
+
+let cursor_next_lwt cursor acc f =
+  match Lmdb.cursor_next cursor with
+  | Error KeyNotFound -> acc
+  | Error err -> lwt_fail_error err
+  | Ok () -> Lwt.bind acc f
+
 let fold t k ~init ~f =
-  let k_concat = concat k in
   let base_len = List.length k in
-  let i = LevelDB.Iterator.make t in
-  LevelDB.Iterator.seek i k_concat 0 (String.length k_concat) ;
-  let returned = Hashtbl.create 31 in
-  let rec inner acc =
-    match LevelDB.Iterator.valid i with
+  let rec inner ht cursor acc =
+    Lmdb.cursor_get cursor >>=? fun (kk, _v) ->
+    let kk = MBytes.to_string kk in
+    let kk_split = split kk in
+    match is_child ~child:kk_split ~parent:k with
     | false -> Lwt.return acc
     | true ->
-        let kk = LevelDB.Iterator.get_key i in
-        let kk_split = split kk in
-        match is_child ~child:kk_split ~parent:k with
-        | false -> Lwt.return acc
-        | true ->
-            let cur_len = List.length kk_split in
-            LevelDB.Iterator.next i ;
-            if cur_len = succ base_len then begin
-              (f (`Key kk_split) acc) >>= inner
-            end
-            else begin
-              let dir = list_sub kk_split 0 (succ base_len) in
-              if Hashtbl.mem returned dir then
-                inner acc
-              else begin
-                Hashtbl.add returned dir () ;
-                (f (`Dir dir) acc) >>= inner
-              end
-            end ;
-  in
-  inner init
+        let cur_len = List.length kk_split in
+        if cur_len = succ base_len then begin
+          cursor_next_lwt cursor (f (`Key kk_split) acc) (inner ht cursor)
+        end
+        else begin
+          let dir = list_sub kk_split 0 (succ base_len) in
+          if Hashtbl.mem ht dir then
+            cursor_next_lwt cursor (Lwt.return acc) (inner ht cursor)
+          else begin
+            Hashtbl.add ht dir () ;
+            cursor_next_lwt cursor (f (`Dir dir) acc) (inner ht cursor)
+          end
+        end in
+  with_rw_cursor_lwt t ~f:begin fun cursor ->
+    match Lmdb.cursor_at cursor (concat k) with
+    | Error KeyNotFound -> Lwt.return init
+    | Error err -> lwt_fail_error err
+    | Ok () ->
+        let ht = Hashtbl.create 31 in
+        inner ht cursor init
+  end
 
-let fold_keys s k ~init ~f =
-  let rec loop k acc =
-    fold s k ~init:acc
-      ~f:(fun file acc ->
-          match file with
-          | `Key k -> f k acc
-          | `Dir k -> loop k acc) in
-  loop k init
+let fold_keys t k ~init ~f =
+  with_rw_cursor_lwt t ~f:begin fun cursor ->
+    match Lmdb.cursor_at cursor (concat k) with
+    | Error KeyNotFound -> Lwt.return init
+    | Error err -> lwt_fail_error err
+    | Ok () ->
+        let rec inner acc =
+          Lmdb.cursor_get cursor >>=? fun (kk, _v) ->
+          let kk = MBytes.to_string kk in
+          let kk_split = split kk in
+          match is_child ~child:kk_split ~parent:k with
+          | false -> Lwt.return acc
+          | true -> cursor_next_lwt cursor (f kk_split acc) inner
+        in inner init
+  end
 
-let keys t = fold_keys t ~init:[] ~f:(fun k acc -> Lwt.return (k :: acc))
+let keys t =
+  fold_keys t ~init:[] ~f:(fun k acc -> Lwt.return (k :: acc))
diff --git a/src/lib_storage/raw_store.mli b/src/lib_storage/raw_store.mli
index ace4dc094..202d0f19e 100644
--- a/src/lib_storage/raw_store.mli
+++ b/src/lib_storage/raw_store.mli
@@ -11,6 +11,6 @@ open Store_sigs
 
 include STORE
 
-val init: string -> t tzresult Lwt.t
+val init: ?mapsize:int64 -> string -> t tzresult Lwt.t
 val close : t -> unit
 
diff --git a/src/lib_storage/test/test_context.ml b/src/lib_storage/test/test_context.ml
index 3856b06f5..4a40861ec 100644
--- a/src/lib_storage/test/test_context.ml
+++ b/src/lib_storage/test/test_context.ml
@@ -87,7 +87,7 @@ type t = {
 let wrap_context_init f _ () =
   Lwt_utils_unix.with_tempdir "tezos_test_" begin fun base_dir ->
     let root = base_dir // "context" in
-    Context.init ~root ?patch_context:None >>= fun idx ->
+    Context.init ~mapsize:4_096_000L root >>= fun idx ->
     Context.commit_genesis idx
       ~chain_id
       ~time:genesis_time
diff --git a/src/lib_storage/tezos-storage.opam b/src/lib_storage/tezos-storage.opam
index a82fb41e7..7faa500f0 100644
--- a/src/lib_storage/tezos-storage.opam
+++ b/src/lib_storage/tezos-storage.opam
@@ -10,8 +10,8 @@ depends: [
   "ocamlfind" { build }
   "jbuilder" { build & = "1.0+beta20" }
   "tezos-base"
-  "leveldb"
-  "irmin-leveldb"
+  "lmdb"
+  "irmin-lmdb"
   "tezos-stdlib-unix" { test }
   "alcotest-lwt" { test }
 ]