diff --git a/src/inc/taoserror.h b/src/inc/taoserror.h
index ff91989e5f..b99bf2df2a 100644
--- a/src/inc/taoserror.h
+++ b/src/inc/taoserror.h
@@ -389,6 +389,14 @@ TAOS_DEFINE_ERROR(TSDB_CODE_ODBC_CONV_SRC_BAD_SEQ,        0, 0x2113, "src bad se
 TAOS_DEFINE_ERROR(TSDB_CODE_ODBC_CONV_SRC_INCOMPLETE,     0, 0x2114, "src incomplete")
 TAOS_DEFINE_ERROR(TSDB_CODE_ODBC_CONV_SRC_GENERAL,        0, 0x2115, "src general")
 
+// tfs
+TAOS_DEFINE_ERROR(TSDB_CODE_FS_OUT_OF_MEMORY,             0, 0x2200, "tfs out of memory")
+TAOS_DEFINE_ERROR(TSDB_CODE_FS_INVLD_CFG                  0, 0x2201, "tfs invalid mount config")
+TAOS_DEFINE_ERROR(TSDB_CODE_FS_TOO_MANY_MOUNT             0, 0x2202, "tfs too many mount")
+TAOS_DEFINE_ERROR(TSDB_CODE_FS_DUP_PRIMARY                0, 0x2203, "tfs duplicate primary mount")
+TAOS_DEFINE_ERROR(TSDB_CODE_FS_NO_PRIMARY_DISK            0, 0x2204, "tfs no primary mount")
+TAOS_DEFINE_ERROR(TSDB_CODE_FS_NO_MOUNT_AT_TIER           0, 0x2205, "tfs no mount at tier")
+
 
 #ifdef TAOS_ERROR_C
 };
diff --git a/src/tfs/inc/tdisk.h b/src/tfs/inc/tdisk.h
index f15512355d..bfbf9dc474 100644
--- a/src/tfs/inc/tdisk.h
+++ b/src/tfs/inc/tdisk.h
@@ -16,6 +16,8 @@
 #ifndef TD_TDISK_H
 #define TD_TDISK_H
 
+#include "tfslog.h"
+
 #ifdef __cplusplus
 extern "C" {
 #endif
diff --git a/src/tfs/inc/tfslog.h b/src/tfs/inc/tfslog.h
new file mode 100644
index 0000000000..68c2111dc9
--- /dev/null
+++ b/src/tfs/inc/tfslog.h
@@ -0,0 +1,34 @@
+/*
+ * Copyright (c) 2019 TAOS Data, Inc. <jhtao@taosdata.com>
+ *
+ * This program is free software: you can use, redistribute, and/or modify
+ * it under the terms of the GNU Affero General Public License, version 3
+ * or later ("AGPL"), as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef TD_TFSLOG_H
+#define TD_TFSLOG_H
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#define fFatal(...) { if (fsDebugFlag & DEBUG_FATAL) { taosPrintLog("FS FATAL ", 255, __VA_ARGS__); }}
+#define fError(...) { if (fsDebugFlag & DEBUG_ERROR) { taosPrintLog("FS ERROR ", 255, __VA_ARGS__); }}
+#define fWarn(...)  { if (fsDebugFlag & DEBUG_WARN)  { taosPrintLog("FS WARN ", 255, __VA_ARGS__); }}
+#define fInfo(...)  { if (fsDebugFlag & DEBUG_INFO)  { taosPrintLog("FS ", 255, __VA_ARGS__); }}
+#define fDebug(...) { if (fsDebugFlag & DEBUG_DEBUG) { taosPrintLog("FS ", cqDebugFlag, __VA_ARGS__); }}
+#define fTrace(...) { if (fsDebugFlag & DEBUG_TRACE) { taosPrintLog("FS ", cqDebugFlag, __VA_ARGS__); }}
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif
\ No newline at end of file
diff --git a/src/tfs/inc/ttier.h b/src/tfs/inc/ttier.h
index f406e3d8c2..3809890272 100644
--- a/src/tfs/inc/ttier.h
+++ b/src/tfs/inc/ttier.h
@@ -30,7 +30,7 @@ typedef struct {
   SDisk *disks[TSDB_MAX_DISK_PER_TIER];
 } STier;
 
-#define DISK_AT_TIER(pTier, id) ((pTier)->disks + (id))
+#define DISK_AT_TIER(pTier, id) ((pTier)->disks[id])
 
 void   tdInitTier(STier *pTier, int level);
 void   tdDestroyTier(STier *pTier);
diff --git a/src/tfs/src/tdisk.c b/src/tfs/src/tdisk.c
index 83dfbb1b06..f8d7cf34dd 100644
--- a/src/tfs/src/tdisk.c
+++ b/src/tfs/src/tdisk.c
@@ -14,6 +14,7 @@
  */
 
 #include "tdisk.h"
+#include "taoserror.h"
 
 SDisk *tdNewDisk(int level, int id, char *dir) {
   SDisk *pDisk = (SDisk *)calloc(1, sizeof(*pDisk));
diff --git a/src/tfs/src/tfs.c b/src/tfs/src/tfs.c
index 09c6a7e707..63c9d056ae 100644
--- a/src/tfs/src/tfs.c
+++ b/src/tfs/src/tfs.c
@@ -14,17 +14,12 @@
  */
 
 #include "os.h"
-#include "hash.h"
-#include "ttier.h"
-#include "tglobal.h"
-#include "taoserror.h"
 
-#define fFatal(...) { if (fsDebugFlag & DEBUG_FATAL) { taosPrintLog("FS FATAL ", 255, __VA_ARGS__); }}
-#define fError(...) { if (fsDebugFlag & DEBUG_ERROR) { taosPrintLog("FS ERROR ", 255, __VA_ARGS__); }}
-#define fWarn(...)  { if (fsDebugFlag & DEBUG_WARN)  { taosPrintLog("FS WARN ", 255, __VA_ARGS__); }}
-#define fInfo(...)  { if (fsDebugFlag & DEBUG_INFO)  { taosPrintLog("FS ", 255, __VA_ARGS__); }}
-#define fDebug(...) { if (fsDebugFlag & DEBUG_DEBUG) { taosPrintLog("FS ", cqDebugFlag, __VA_ARGS__); }}
-#define fTrace(...) { if (fsDebugFlag & DEBUG_TRACE) { taosPrintLog("FS ", cqDebugFlag, __VA_ARGS__); }}
+#include "hash.h"
+#include "taoserror.h"
+#include "tfs.h"
+#include "tglobal.h"
+#include "ttier.h"
 
 #define TSDB_MAX_TIER 3
 
@@ -69,7 +64,7 @@ int tfsInit(SDiskCfg *pDiskCfg, int ndisk) {
   }
 
   for (int idisk = 0; idisk < ndisk; idisk++) {
-    if (tfsAddDisk(pDiskCfg + idisk) < 0) {
+    if (tfsMount(pDiskCfg + idisk) < 0) {
       tfsDestroy();
       return -1;
     }
@@ -106,7 +101,7 @@ int tfsUpdateInfo() {
 }
 
 void tfsPrimaryPath(char *dst) {
-  strncpy(dst, DISK_AT)
+  strncpy(dst, DISK_AT(0, 0)->dir, TSDB_FILENAME_LEN);
 }
 
 int tfsCreateDir(char *name) {
@@ -131,16 +126,23 @@ int tfsCreateDir(char *name) {
   return 0;
 }
 
-static int tfsAddDisk(SDiskCfg *pCfg) {
+static int tfsMount(SDiskCfg *pCfg) {
+  SDiskID did;
+
   if (tfsCheckAndFormatCfg(pCfg) < 0) return -1;
 
-  if (tdAddDiskToTier(pCfg, TIER_AT(pCfg->level)) < 0) {
+  did.level = pCfg->level;
+  did.id = tdAddDiskToTier(TIER_AT(pCfg->level), pCfg);
+  if (did.id < 0) {
     fError("failed to add disk %s to FS since %s", pCfg->dir, tstrerror(terrno));
+    return -1;
   }
 
-  taosHashPut(pTiers->map, (void *)dirName, strnlen(dirName, TSDB_FILENAME_LEN), (void *)(&diskid), sizeof(diskid));
+  taosHashPut(pTiers->map, pCfg->dir, strnlen(pCfg->dir, TSDB_FILENAME_LEN), (void *)(&did), sizeof(did));
   if (pfs->nlevel < pCfg->level + 1) pfs->nlevel = pCfg->level + 1;
 
+  // TODO: update meta info
+
   return 0;
 }
 
@@ -154,12 +156,19 @@ static int tfsCheckAndFormatCfg(SDiskCfg *pCfg) {
     return -1;
   }
 
-  if (pCfg->primary && pCfg->level != 0) {
-    fError("failed to add disk %s to FS since disk is primary but level %d not 0", pCfg->dir, pCfg->level);
-    terrno = TSDB_CODE_FS_INVLD_CFG;
-    return -1;
-  }
+  if (pCfg->primary) {
+    if (pCfg->level != 0) {
+      fError("failed to add disk %s to FS since disk is primary but level %d not 0", pCfg->dir, pCfg->level);
+      terrno = TSDB_CODE_FS_INVLD_CFG;
+      return -1;
+    }
 
+    if (DISK_AT(0, 0) != NULL) {
+      fError("failed to add disk %s to FS since duplicate primary mount", pCfg->dir, pCfg->level);
+      terrno = TSDB_CODE_FS_DUP_PRIMARY;
+      return -1;
+    }
+  }
 
   if (tfsFormatDir(pCfg->dir, dirName) < 0) {
     fError("failed to add disk %s to FS since invalid dir format", pCfg->dir);
@@ -167,14 +176,14 @@ static int tfsCheckAndFormatCfg(SDiskCfg *pCfg) {
     return -1;
   }
 
-  if (tdGetDiskByName(dirName)) {
-    fError("failed to add disk %s to FS since duplicate add", pCfg->dir);
+  if (tfsGetDiskByName(dirName) != NULL) {
+    fError("failed to add disk %s to FS since duplicate mount", pCfg->dir);
     terrno = TSDB_CODE_FS_INVLD_CFG;
     return -1;
   }
 
   if (access(dirName, W_OK | R_OK | F_OK) != 0) {
-    fError("failed to add disk %s to FS since no enough access rights", pCfg->dir);
+    fError("failed to add disk %s to FS since no R/W access rights", pCfg->dir);
     terrno = TSDB_CODE_FS_INVLD_CFG;
     return -1;
   }
@@ -223,13 +232,14 @@ static int tfsCheck() {
     return -1;
   }
 
-  for (int level = 0; level < pfs->nlevel; level++) {
+  int level = 0;
+  do {
     if (TIER_AT(level)->ndisk == 0) {
       fError("no disk at level %d", level);
-      terrno = TSDB_CODE_FS_NO_DISK_AT_TIER;
+      terrno = TSDB_CODE_FS_NO_MOUNT_AT_TIER;
       return -1;
     }
-  }
+  } while (level < pfs->nlevel);
 
   return 0;
 }
@@ -252,4 +262,9 @@ static tfsUnLock() {
   }
 
   return 0;
-}
\ No newline at end of file
+}
+
+static tfsGetDiskByName(char *dirName) {
+}
+
+static SDisk *tfsGetDiskByID(SDiskID did) { return DISK_AT(did.level, did.id); }
\ No newline at end of file
diff --git a/src/tfs/src/ttier.c b/src/tfs/src/ttier.c
index 11fb067682..10db8678ec 100644
--- a/src/tfs/src/ttier.c
+++ b/src/tfs/src/ttier.c
@@ -15,6 +15,7 @@
 
 #include "ttier.h"
 #include "tglobal.h"
+#include "taoserror.h"
 
 void tdInitTier(STier *pTier, int level) {
   pTier->level = level;
@@ -23,8 +24,9 @@ void tdInitTier(STier *pTier, int level) {
 void tdDestroyTier(STier *pTier) {
   for (int id = 0; id < TSDB_MAX_DISK_PER_TIER; id++) {
     tdFreeDisk(DISK_AT_TIER(pTier, id));
-    DISK_AT_TIER(pTier, id) = NULL;
+    pTier->disks[id] = NULL;
   }
+  pTier->ndisk = 0;
 }
 
 SDisk *tdAddDiskToTier(STier *pTier, SDiskCfg *pCfg) {
@@ -32,35 +34,29 @@ SDisk *tdAddDiskToTier(STier *pTier, SDiskCfg *pCfg) {
   int id = 0;
 
   if (pTier->ndisk >= TSDB_MAX_DISK_PER_TIER) {
-    terrno = TSDB_CODE_FS_TOO_MANY_DISKS;
+    terrno = TSDB_CODE_FS_TOO_MANY_MOUNT;
     return -1;
   }
 
-  if (pCfg->primary) {
-    if (DISK_AT(0, 0) != NULL) {
-      terrno = TSDB_CODE_FS_DUP_PRIMARY;
-      return -1;
+  if (pTier->level == 0) {
+    if (DISK_AT_TIER(pTier, 0) != NULL) {
+      id = pTier->ndisk;
+    } else {
+      id = pTier->ndisk + 1;
+      if (id >= TSDB_MAX_DISK_PER_TIER) {
+        terrno = TSDB_CODE_FS_TOO_MANY_MOUNT;
+        return -1;
+      }
     }
   } else {
-    if (pTier->level == 0) {
-      if (DISK_AT_TIER(pTier, 0) != NULL) {
-        id = pTier->ndisk;
-      } else {
-        id = pTier->ndisk + 1;
-        if (id >= TSDB_MAX_DISK_PER_TIER) {
-          terrno = TSDB_CODE_FS_TOO_MANY_DISKS;
-          return -1;
-        }
-      }
-    } else {
-      id = pTier->ndisk;
-    }
+    id = pTier->ndisk;
   }
 
   pTier->disks[id] = tdNewDisk(pCfg->level, id, pCfg->dir);
   if (pTier->disks[id] == NULL) return -1;
+  pTier->ndisk++;
 
-  return 0;
+  return id;
 }
 
 int tdUpdateTierInfo(STier *pTier) {