diff --git a/source/dnode/vnode/src/tsdb/dev/inc/tsdbFS.h b/source/dnode/vnode/src/tsdb/dev/inc/tsdbFS.h
index 7b989184772bc034c33dfa8a7a5f66d997957812..338dc84e4a03f4e3580d7cefbf5704db94cdd717 100644
--- a/source/dnode/vnode/src/tsdb/dev/inc/tsdbFS.h
+++ b/source/dnode/vnode/src/tsdb/dev/inc/tsdbFS.h
@@ -32,8 +32,8 @@ typedef enum {
 
 /* Exposed APIs */
 // open/close
-int32_t tsdbOpenFS(STsdb *pTsdb, STFileSystem **ppFS, int8_t rollback);
-int32_t tsdbCloseFS(STFileSystem **ppFS);
+int32_t tsdbOpenFS(STsdb *pTsdb, STFileSystem **fs, int8_t rollback);
+int32_t tsdbCloseFS(STFileSystem **fs);
 // txn
 int32_t tsdbFSAllocEid(STFileSystem *pFS, int64_t *eid);
 int32_t tsdbFSEditBegin(STFileSystem *fs, int64_t eid, const SArray *aFileOp, EFEditT etype);
@@ -45,14 +45,14 @@ int32_t tsdbFSGetFSet(STFileSystem *fs, int32_t fid, const STFileSet **ppFSet);
 /* Exposed Structs */
 struct STFileSystem {
   STsdb  *pTsdb;
-  int32_t state;
   tsem_t  canEdit;
+  int32_t state;
   int64_t neid;
   SArray *cstate;  // current state, SArray<STFileSet>
   // new state
   EFEditT etype;
   int64_t eid;
-  SArray *nstate;  // next state, SArray<STFileSet>
+  SArray *nstate;  // staging state, SArray<STFileSet>
 };
 
 #ifdef __cplusplus
diff --git a/source/dnode/vnode/src/tsdb/dev/inc/tsdbFSet.h b/source/dnode/vnode/src/tsdb/dev/inc/tsdbFSet.h
index 30de41b7f749b65a71d042a8f53fb570f4863dbd..40c3de2e1d7f90394a76fda5e5f1f1bd7eb6bf62 100644
--- a/source/dnode/vnode/src/tsdb/dev/inc/tsdbFSet.h
+++ b/source/dnode/vnode/src/tsdb/dev/inc/tsdbFSet.h
@@ -52,9 +52,9 @@ struct STFileOp {
 
 typedef struct SSttLvl {
   SRBTreeNode rbtn;
-  int32_t     lvl;   // level
-  int32_t     nstt;  // number of .stt files on this level
-  STFile     *fstt;  // .stt files
+  int32_t     lvl;      // level
+  int32_t     nstt;     // number of .stt files on this level
+  SRBTree     sttTree;  // .stt file tree, sorted by cid
 } SSttLvl;
 
 struct STFileSet {
diff --git a/source/dnode/vnode/src/tsdb/dev/inc/tsdbFile.h b/source/dnode/vnode/src/tsdb/dev/inc/tsdbFile.h
index b1b08d7661a04bd48cadecdcf9baf2e1947c0b91..64b7b0b2aebde93a0618c5e602905d750864b03c 100644
--- a/source/dnode/vnode/src/tsdb/dev/inc/tsdbFile.h
+++ b/source/dnode/vnode/src/tsdb/dev/inc/tsdbFile.h
@@ -47,12 +47,9 @@ int32_t tsdbTFileInit(STsdb *pTsdb, STFile *pFile);
 int32_t tsdbTFileClear(STFile *pFile);
 
 struct STFile {
-  LISTD(STFile) listNode;
-  int32_t ref;
-
   char         fname[TSDB_FILENAME_LEN];
   tsdb_ftype_t type;
-  SDiskID      did;
+  SDiskID      did;  // disk id
   int32_t      fid;  // file id
   int64_t      cid;  // commit id
   int64_t      size;
@@ -64,6 +61,12 @@ struct STFile {
   };
 };
 
+struct STFileObj {
+  SRBTreeNode rbtn;
+  int32_t     ref;
+  STFile      f;
+};
+
 #ifdef __cplusplus
 }
 #endif
diff --git a/source/dnode/vnode/src/tsdb/dev/tsdbFS.c b/source/dnode/vnode/src/tsdb/dev/tsdbFS.c
index aaf814e35fd422383214c5415df3fa7e14f815f7..287eb493917e344715cb917569a7d2970ec43867 100644
--- a/source/dnode/vnode/src/tsdb/dev/tsdbFS.c
+++ b/source/dnode/vnode/src/tsdb/dev/tsdbFS.c
@@ -37,36 +37,34 @@ static const char *gCurrentFname[] = {
     [TSDB_FCURRENT_M] = "current.m.json",
 };
 
-static int32_t create_fs(STsdb *pTsdb, STFileSystem **ppFS) {
-  ppFS[0] = taosMemoryCalloc(1, sizeof(*ppFS[0]));
-  if (ppFS[0] == NULL) {
+static int32_t create_fs(STsdb *pTsdb, STFileSystem **fs) {
+  fs[0] = taosMemoryCalloc(1, sizeof(*fs[0]));
+  if (fs[0] == NULL) return TSDB_CODE_OUT_OF_MEMORY;
+
+  fs[0]->cstate = taosArrayInit(16, sizeof(STFileSet));
+  fs[0]->nstate = taosArrayInit(16, sizeof(STFileSet));
+  if (fs[0]->cstate == NULL || fs[0]->nstate == NULL) {
+    taosArrayDestroy(fs[0]->nstate);
+    taosArrayDestroy(fs[0]->cstate);
+    taosMemoryFree(fs[0]);
     return TSDB_CODE_OUT_OF_MEMORY;
   }
 
-  ppFS[0]->cstate = taosArrayInit(16, sizeof(STFileSet));
-  ppFS[0]->nstate = taosArrayInit(16, sizeof(STFileSet));
-  if (ppFS[0]->cstate == NULL || ppFS[0]->nstate == NULL) {
-    taosArrayDestroy(ppFS[0]->nstate);
-    taosArrayDestroy(ppFS[0]->cstate);
-    taosMemoryFree(ppFS[0]);
-    return TSDB_CODE_OUT_OF_MEMORY;
-  }
-
-  ppFS[0]->pTsdb = pTsdb;
-  ppFS[0]->state = TSDB_FS_STATE_NONE;
-  tsem_init(&ppFS[0]->canEdit, 0, 1);
-  ppFS[0]->neid = 0;
+  fs[0]->pTsdb = pTsdb;
+  fs[0]->state = TSDB_FS_STATE_NONE;
+  tsem_init(&fs[0]->canEdit, 0, 1);
+  fs[0]->neid = 0;
 
   return 0;
 }
 
-static int32_t destroy_fs(STFileSystem **ppFS) {
-  if (ppFS[0] == NULL) return 0;
-  taosArrayDestroy(ppFS[0]->nstate);
-  taosArrayDestroy(ppFS[0]->cstate);
-  tsem_destroy(&ppFS[0]->canEdit);
-  taosMemoryFree(ppFS[0]);
-  ppFS[0] = NULL;
+static int32_t destroy_fs(STFileSystem **fs) {
+  if (fs[0] == NULL) return 0;
+  taosArrayDestroy(fs[0]->nstate);
+  taosArrayDestroy(fs[0]->cstate);
+  tsem_destroy(&fs[0]->canEdit);
+  taosMemoryFree(fs[0]);
+  fs[0] = NULL;
   return 0;
 }
 
@@ -398,7 +396,7 @@ static int32_t open_fs(STFileSystem *fs, int8_t rollback) {
     code = scan_and_fix_fs(fs);
     TSDB_CHECK_CODE(code, lino, _exit);
   } else {
-    code = save_fs(0, fs->nstate, fCurrent);
+    code = save_fs(0, fs->cstate, fCurrent);
     TSDB_CHECK_CODE(code, lino, _exit);
   }
 
@@ -470,20 +468,20 @@ _exit:
   return 0;
 }
 
-int32_t tsdbOpenFS(STsdb *pTsdb, STFileSystem **ppFS, int8_t rollback) {
+int32_t tsdbOpenFS(STsdb *pTsdb, STFileSystem **fs, int8_t rollback) {
   int32_t code;
   int32_t lino;
 
-  code = create_fs(pTsdb, ppFS);
+  code = create_fs(pTsdb, fs);
   TSDB_CHECK_CODE(code, lino, _exit);
 
-  code = open_fs(ppFS[0], rollback);
+  code = open_fs(fs[0], rollback);
   TSDB_CHECK_CODE(code, lino, _exit)
 
 _exit:
   if (code) {
     tsdbError("vgId:%d %s failed at line %d since %s", TD_VID(pTsdb->pVnode), __func__, lino, tstrerror(code));
-    destroy_fs(ppFS);
+    destroy_fs(fs);
   } else {
     tsdbInfo("vgId:%d %s success", TD_VID(pTsdb->pVnode), __func__);
   }
diff --git a/source/dnode/vnode/src/tsdb/dev/tsdbFSet.c b/source/dnode/vnode/src/tsdb/dev/tsdbFSet.c
index 8d362360642f5de0e5161db89aa83fb499d19fbd..fb904072b035e5e851f65c37b9953292086c8b8d 100644
--- a/source/dnode/vnode/src/tsdb/dev/tsdbFSet.c
+++ b/source/dnode/vnode/src/tsdb/dev/tsdbFSet.c
@@ -47,8 +47,8 @@ static int32_t add_file(STFileSet *fset, STFile *f) {
   if (f->type == TSDB_FTYPE_STT) {
     SSttLvl *lvl = NULL;  // TODO
 
-    lvl->nstt++;
-    lvl->fstt = f;
+    // lvl->nstt++;
+    // lvl->fstt = f;
   } else {
     fset->farr[f->type] = f;
   }
diff --git a/source/dnode/vnode/src/tsdb/dev/tsdbFile.c b/source/dnode/vnode/src/tsdb/dev/tsdbFile.c
index fd9a84d9bc39d3edeab6c66c323cc08d3b686ae7..5a1ab084487456a1bc13ec82eca96ced550593f4 100644
--- a/source/dnode/vnode/src/tsdb/dev/tsdbFile.c
+++ b/source/dnode/vnode/src/tsdb/dev/tsdbFile.c
@@ -193,7 +193,7 @@ int32_t tsdbTFileInit(STsdb *pTsdb, STFile *pFile) {
              pFile->cid,                     //
              g_tfile_info[pFile->type].suffix);
   }
-  pFile->ref = 1;
+  // pFile->ref = 1;
   return 0;
 }
 
@@ -235,7 +235,7 @@ int32_t tsdbTFileCreate(const STFile *pFile, STFile **f) {
 
   *f[0] = *pFile;
 
-  f[0]->ref = 1;
+  // f[0]->ref = 1;
   return 0;
 }