diff --git a/source/dnode/mnode/impl/src/mndSync.c b/source/dnode/mnode/impl/src/mndSync.c
index b53b3003c18337b2abf892fdbb648366876f00fd..e25aa468bff66f1deb6cb089ed3887518483a805 100644
--- a/source/dnode/mnode/impl/src/mndSync.c
+++ b/source/dnode/mnode/impl/src/mndSync.c
@@ -17,12 +17,12 @@
 #include "mndSync.h"
 #include "mndTrans.h"
 
-int32_t mndSyncEqMsg(const SMsgCb *msgcb, SRpcMsg *pMsg) { 
+int32_t mndSyncEqMsg(const SMsgCb *msgcb, SRpcMsg *pMsg) {
   SMsgHead *pHead = pMsg->pCont;
   pHead->contLen = htonl(pHead->contLen);
   pHead->vgId = htonl(pHead->vgId);
 
-  return tmsgPutToQueue(msgcb, SYNC_QUEUE, pMsg); 
+  return tmsgPutToQueue(msgcb, SYNC_QUEUE, pMsg);
 }
 
 int32_t mndSyncSendMsg(const SEpSet *pEpSet, SRpcMsg *pMsg) { return tmsgSendReq(pEpSet, pMsg); }
@@ -32,7 +32,7 @@ void mndSyncCommitMsg(struct SSyncFSM *pFsm, const SRpcMsg *pMsg, SFsmCbMeta cbM
   SSyncMgmt *pMgmt = &pMnode->syncMgmt;
   SSdbRaw   *pRaw = pMsg->pCont;
 
-  int32_t transId = sdbGetIdFromRaw(pRaw);
+  int32_t transId = sdbGetIdFromRaw(pMnode->pSdb, pRaw);
   pMgmt->errCode = cbMeta.code;
   mTrace("trans:%d, is proposed, savedTransId:%d code:0x%x, ver:%" PRId64 " term:%" PRId64 " role:%s raw:%p", transId,
          pMgmt->transId, cbMeta.code, cbMeta.index, cbMeta.term, syncStr(cbMeta.state), pRaw);
@@ -67,24 +67,37 @@ void mndRestoreFinish(struct SSyncFSM *pFsm) {
   }
 }
 
-int32_t mndSnapshotRead(struct SSyncFSM* pFsm, const SSnapshot* pSnapshot, void** ppIter, char** ppBuf, int32_t* len) {
-  /*
+int32_t mndSnapshotRead(struct SSyncFSM *pFsm, const SSnapshot *pSnapshot, void **ppIter, char **ppBuf, int32_t *len) {
   SMnode *pMnode = pFsm->data;
-  SSdbIter *pIter;
-  if (iter == NULL) { 
-    pIter = sdbIterInit(pMnode->sdb)
+  mInfo("start to read snapshot from sdb");
+
+  int32_t code = sdbReadSnapshot(pMnode->pSdb, (SSdbIter **)ppIter, ppBuf, len);
+  if (code != 0) {
+    mError("failed to read snapshot from sdb since %s", terrstr());
   } else {
-    pIter = iter;
+    if (*ppIter == NULL) {
+      mInfo("successfully to read snapshot from sdb");
+    }
   }
-  */
 
-  return 0;
+  return code;
 }
 
-int32_t mndSnapshotApply(struct SSyncFSM* pFsm, const SSnapshot* pSnapshot, char* pBuf, int32_t len) {
+int32_t mndSnapshotApply(struct SSyncFSM *pFsm, const SSnapshot *pSnapshot, char *pBuf, int32_t len) {
   SMnode *pMnode = pFsm->data;
-  sdbWrite(pMnode->pSdb, (SSdbRaw*)pBuf);
-  return 0;
+  pMnode->syncMgmt.restored = false;
+  mInfo("start to apply snapshot to sdb, len:%d", len);
+
+  int32_t code = sdbApplySnapshot(pMnode->pSdb, pBuf, len);
+  if (code != 0) {
+    mError("failed to apply snapshot to sdb, len:%d", len);
+  } else {
+    mInfo("successfully to apply snapshot to sdb, len:%d", len);
+    pMnode->syncMgmt.restored = true;
+  }
+
+  // taosMemoryFree(pBuf);
+  return code;
 }
 
 void mndReConfig(struct SSyncFSM *pFsm, SSyncCfg newCfg, SReConfigCbMeta cbMeta) {
@@ -116,7 +129,7 @@ SSyncFSM *mndSyncMakeFsm(SMnode *pMnode) {
   pFsm->FpSnapshotRead = mndSnapshotRead;
   pFsm->FpSnapshotApply = mndSnapshotApply;
   pFsm->FpReConfigCb = mndReConfig;
-  
+
   return pFsm;
 }
 
@@ -150,8 +163,7 @@ int32_t mndInitSync(SMnode *pMnode) {
   SSyncCfg *pCfg = &syncInfo.syncCfg;
   pCfg->replicaNum = pMnode->replica;
   pCfg->myIndex = pMnode->selfIndex;
-  mInfo("start to open mnode sync, replica:%d myindex:%d standby:%d", pCfg->replicaNum, pCfg->myIndex,
-        pMgmt->standby);
+  mInfo("start to open mnode sync, replica:%d myindex:%d standby:%d", pCfg->replicaNum, pCfg->myIndex, pMgmt->standby);
   for (int32_t i = 0; i < pMnode->replica; ++i) {
     SNodeInfo *pNode = &pCfg->nodeInfo[i];
     tstrncpy(pNode->nodeFqdn, pMnode->replicas[i].fqdn, sizeof(pNode->nodeFqdn));
diff --git a/source/dnode/mnode/sdb/inc/sdb.h b/source/dnode/mnode/sdb/inc/sdb.h
index 3932defd8db79e0a83cfec078c01e8a97e0ec3d5..32e29f5e1c6082e8a3823b2f180d90f997fe73ac 100644
--- a/source/dnode/mnode/sdb/inc/sdb.h
+++ b/source/dnode/mnode/sdb/inc/sdb.h
@@ -186,7 +186,7 @@ typedef struct SSdb {
 
 typedef struct SSdbIter {
   TdFilePtr file;
-  int64_t   readlen;
+  int64_t   total;
 } SSdbIter;
 
 typedef struct {
@@ -380,13 +380,12 @@ SSdbRow *sdbAllocRow(int32_t objSize);
 void    *sdbGetRowObj(SSdbRow *pRow);
 void     sdbFreeRow(SSdb *pSdb, SSdbRow *pRow, bool callFunc);
 
-SSdbIter *sdbIterInit(SSdb *pSdb);
-SSdbIter *sdbIterRead(SSdb *pSdb, SSdbIter *iter, char **ppBuf, int32_t *len);
+int32_t sdbReadSnapshot(SSdb *pSdb, SSdbIter **ppIter, char **ppBuf, int32_t *len);
+int32_t sdbApplySnapshot(SSdb *pSdb, char *pBuf, int32_t len);
 
 const char *sdbTableName(ESdbType type);
 void        sdbPrintOper(SSdb *pSdb, SSdbRow *pRow, const char *oper);
-
-int32_t sdbGetIdFromRaw(SSdbRaw *pRaw);
+int32_t     sdbGetIdFromRaw(SSdb *pSdb, SSdbRaw *pRaw);
 
 #ifdef __cplusplus
 }
diff --git a/source/dnode/mnode/sdb/inc/sdbInt.h b/source/dnode/mnode/sdb/inc/sdbInt.h
deleted file mode 100644
index c49d6e8fb287619d9503282dd2e164ed432ce823..0000000000000000000000000000000000000000
--- a/source/dnode/mnode/sdb/inc/sdbInt.h
+++ /dev/null
@@ -1,61 +0,0 @@
-/*
- * 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_SDB_INT_H_
-#define _TD_SDB_INT_H_
-
-#include "os.h"
-
-#include "sdb.h"
-
-#ifdef __cplusplus
-extern "C" {
-#endif
-
-// clang-format off
-#define mFatal(...) { if (mDebugFlag & DEBUG_FATAL) { taosPrintLog("MND FATAL ", DEBUG_FATAL, 255, __VA_ARGS__); }}
-#define mError(...) { if (mDebugFlag & DEBUG_ERROR) { taosPrintLog("MND ERROR ", DEBUG_ERROR, 255, __VA_ARGS__); }}
-#define mWarn(...)  { if (mDebugFlag & DEBUG_WARN)  { taosPrintLog("MND WARN ", DEBUG_WARN, 255, __VA_ARGS__); }}
-#define mInfo(...)  { if (mDebugFlag & DEBUG_INFO)  { taosPrintLog("MND ", DEBUG_INFO, 255, __VA_ARGS__); }}
-#define mDebug(...) { if (mDebugFlag & DEBUG_DEBUG) { taosPrintLog("MND ", DEBUG_DEBUG, mDebugFlag, __VA_ARGS__); }}
-#define mTrace(...) { if (mDebugFlag & DEBUG_TRACE) { taosPrintLog("MND ", DEBUG_TRACE, mDebugFlag, __VA_ARGS__); }}
-// clang-format on
-
-typedef struct SSdbRaw {
-  int8_t  type;
-  int8_t  status;
-  int8_t  sver;
-  int8_t  reserved;
-  int32_t dataLen;
-  char    pData[];
-} SSdbRaw;
-
-typedef struct SSdbRow {
-  ESdbType   type;
-  ESdbStatus status;
-  int32_t    refCount;
-  char       pObj[];
-} SSdbRow;
-
-const char *sdbTableName(ESdbType type);
-void        sdbPrintOper(SSdb *pSdb, SSdbRow *pRow, const char *oper);
-
-void sdbFreeRow(SSdb *pSdb, SSdbRow *pRow, bool callFunc);
-
-#ifdef __cplusplus
-}
-#endif
-
-#endif /*_TD_SDB_INT_H_*/
diff --git a/source/dnode/mnode/sdb/src/sdbFile.c b/source/dnode/mnode/sdb/src/sdbFile.c
index 25cda199568592ba809e76c92e32107a30a163da..46abd5e8b2957f8813666a4553a7e3d37998cd8d 100644
--- a/source/dnode/mnode/sdb/src/sdbFile.c
+++ b/source/dnode/mnode/sdb/src/sdbFile.c
@@ -393,7 +393,7 @@ int32_t sdbDeploy(SSdb *pSdb) {
   return 0;
 }
 
-SSdbIter *sdbIterInit(SSdb *pSdb) {
+static SSdbIter *sdbOpenIter(SSdb *pSdb) {
   char datafile[PATH_MAX] = {0};
   char tmpfile[PATH_MAX] = {0};
   snprintf(datafile, sizeof(datafile), "%s%ssdb.data", pSdb->currDir, TD_DIRSEP);
@@ -414,44 +414,140 @@ SSdbIter *sdbIterInit(SSdb *pSdb) {
   pIter->file = taosOpenFile(tmpfile, TD_FILE_READ);
   if (pIter->file == NULL) {
     terrno = TAOS_SYSTEM_ERROR(errno);
-    mError("failed to read snapshot file:%s since %s", tmpfile, terrstr());
+    mError("failed to read file:%s since %s", tmpfile, terrstr());
     taosMemoryFree(pIter);
     return NULL;
   }
 
-  mDebug("start to read snapshot file:%s, iter:%p", tmpfile, pIter);
   return pIter;
 }
 
-SSdbIter *sdbIterRead(SSdb *pSdb, SSdbIter *pIter, char **ppBuf, int32_t *buflen) {
+static void sdbCloseIter(SSdbIter *pIter) {
+  if (pIter == NULL) return;
+  if (pIter->file != NULL) {
+    taosCloseFile(&pIter->file);
+  }
+  taosMemoryFree(pIter);
+  mInfo("sdbiter:%p, is closed", pIter);
+}
+
+static SSdbIter *sdbGetIter(SSdb *pSdb, SSdbIter **ppIter) {
+  SSdbIter *pIter = NULL;
+  if (ppIter != NULL) pIter = *ppIter;
+
+  if (pIter == NULL) {
+    pIter = sdbOpenIter(pSdb);
+    if (pIter != NULL) {
+      mInfo("sdbiter:%p, is created to read snapshot", pIter);
+      *ppIter = pIter;
+    } else {
+      mError("failed to create sdbiter to read snapshot since %s", terrstr());
+      *ppIter = NULL;
+      return NULL;
+    }
+  } else {
+    mInfo("sdbiter:%p, continue to read snapshot, total:%" PRId64, pIter, pIter->total);
+  }
+
+  return pIter;
+}
+
+int32_t sdbReadSnapshot(SSdb *pSdb, SSdbIter **ppIter, char **ppBuf, int32_t *len) {
   const int32_t maxlen = 100;
 
+  SSdbIter *pIter = sdbGetIter(pSdb, ppIter);
+  if (pIter == NULL) return -1;
+
   char *pBuf = taosMemoryCalloc(1, maxlen);
   if (pBuf == NULL) {
     terrno = TSDB_CODE_OUT_OF_MEMORY;
-    return NULL;
+    sdbCloseIter(pIter);
+    return -1;
   }
 
   int32_t readlen = taosReadFile(pIter->file, pBuf, maxlen);
-  if (readlen == 0) {
-    mTrace("read snapshot to the end, readlen:%" PRId64, pIter->readlen);
-    taosMemoryFree(pBuf);
-    taosCloseFile(&pIter->file);
-    taosMemoryFree(pIter);
-    pIter = NULL;
-  } else if (readlen < 0) {
+  if (readlen < 0 || (readlen == 0 && errno != 0)) {
     terrno = TAOS_SYSTEM_ERROR(errno);
-    mError("failed to read snapshot since %s, readlen:%" PRId64, terrstr(), pIter->readlen);
+    mError("sdbiter:%p, failed to read snapshot since %s, total:%" PRId64, pIter, terrstr(), pIter->total);
+    *ppBuf = NULL;
+    *len = 0;
+    *ppIter = NULL;
+    sdbCloseIter(pIter);
     taosMemoryFree(pBuf);
-    taosCloseFile(&pIter->file);
-    taosMemoryFree(pIter);
-    pIter = NULL;
-  } else {
-    pIter->readlen += readlen;
-    mTrace("read snapshot, readlen:%" PRId64, pIter->readlen);
+    return -1;
+  } else if (readlen == 0) {
+    mInfo("sdbiter:%p, read snapshot to the end, total:%" PRId64, pIter, pIter->total);
+    *ppBuf = NULL;
+    *len = 0;
+    *ppIter = NULL;
+    sdbCloseIter(pIter);
+    taosMemoryFree(pBuf);
+    return 0;
+  } else if ((readlen < maxlen && errno != 0) || readlen == maxlen) {
+    pIter->total += readlen;
+    mInfo("sdbiter:%p, read:%d bytes from snapshot, total:%" PRId64, pIter, readlen, pIter->total);
+    *ppBuf = pBuf;
+    *len = readlen;
+    return 0;
+  } else if (readlen < maxlen && errno == 0) {
+    mInfo("sdbiter:%p, read snapshot to the end, total:%" PRId64, pIter, pIter->total);
     *ppBuf = pBuf;
-    *buflen = readlen;
+    *len = readlen;
+    *ppIter = NULL;
+    sdbCloseIter(pIter);
+    return 0;
+  } else {
+    // impossible
+    mError("sdbiter:%p, read:%d bytes from snapshot, total:%" PRId64, pIter, readlen, pIter->total);
+    *ppBuf = NULL;
+    *len = 0;
+    *ppIter = NULL;
+    sdbCloseIter(pIter);
+    taosMemoryFree(pBuf);
+    return -1;
   }
-
-  return pIter;
 }
+
+int32_t sdbApplySnapshot(SSdb *pSdb, char *pBuf, int32_t len) {
+  char datafile[PATH_MAX] = {0};
+  char tmpfile[PATH_MAX] = {0};
+  snprintf(datafile, sizeof(datafile), "%s%ssdb.data", pSdb->currDir, TD_DIRSEP);
+  snprintf(tmpfile, sizeof(datafile), "%s%ssdb.data", pSdb->tmpDir, TD_DIRSEP);
+
+  TdFilePtr pFile = taosOpenFile(tmpfile, TD_FILE_CREATE | TD_FILE_WRITE | TD_FILE_TRUNC);
+  if (pFile == NULL) {
+    terrno = TAOS_SYSTEM_ERROR(errno);
+    mError("failed to write %s since %s", tmpfile, terrstr());
+    return -1;
+  }
+
+  int32_t writelen = taosWriteFile(pFile, pBuf, len);
+  if (writelen != len) {
+    terrno = TAOS_SYSTEM_ERROR(errno);
+    mError("failed to write %s since %s", tmpfile, terrstr());
+    taosCloseFile(&pFile);
+    return -1;
+  }
+
+  if (taosFsyncFile(pFile) != 0) {
+    terrno = TAOS_SYSTEM_ERROR(errno);
+    mError("failed to fsync %s since %s", tmpfile, terrstr());
+    taosCloseFile(&pFile);
+    return -1;
+  }
+
+  (void)taosCloseFile(&pFile);
+
+  if (taosRenameFile(tmpfile, datafile) != 0) {
+    terrno = TAOS_SYSTEM_ERROR(errno);
+    mError("failed to rename file %s to %s since %s", tmpfile, datafile, terrstr());
+    return -1;
+  }
+
+  if (sdbReadFile(pSdb) != 0) {
+    mError("failed to read from %s since %s", datafile, terrstr());
+    return -1;
+  }
+
+  return 0;
+}
\ No newline at end of file
diff --git a/source/dnode/mnode/sdb/src/sdbRaw.c b/source/dnode/mnode/sdb/src/sdbRaw.c
index 4b61ebb627622bfdb1bb32a1df591d564a7c7b01..90643a54a9de42d4f505fdcb4f1d25ef95b80ac7 100644
--- a/source/dnode/mnode/sdb/src/sdbRaw.c
+++ b/source/dnode/mnode/sdb/src/sdbRaw.c
@@ -16,9 +16,14 @@
 #define _DEFAULT_SOURCE
 #include "sdb.h"
 
-int32_t sdbGetIdFromRaw(SSdbRaw *pRaw) {
-  int32_t id = *((int32_t *)(pRaw->pData));
-  return id;
+int32_t sdbGetIdFromRaw(SSdb *pSdb, SSdbRaw *pRaw) {
+  EKeyType keytype = pSdb->keyTypes[pRaw->type];
+  if (keytype == SDB_KEY_INT32) {
+    int32_t id = *((int32_t *)(pRaw->pData));
+    return id;
+  } else {
+    return -2;
+  }
 }
 
 SSdbRaw *sdbAllocRaw(ESdbType type, int8_t sver, int32_t dataLen) {