diff --git a/include/libs/wal/wal.h b/include/libs/wal/wal.h
index 4d5b4d977a..e77540bf90 100644
--- a/include/libs/wal/wal.h
+++ b/include/libs/wal/wal.h
@@ -18,6 +18,7 @@
 #include "os.h"
 #include "tdef.h"
 #include "tlog.h"
+#include "tarray.h"
 #ifdef __cplusplus
 extern "C" {
 #endif
@@ -39,12 +40,14 @@ typedef enum {
 
 typedef struct {
   int8_t   sver;
-  int8_t   reserved[3];
+  uint8_t  msgType;
+  int8_t   reserved[2];
   int32_t  len;
   int64_t  version;
   uint32_t signature;
-  uint32_t cksum;
-  char     cont[];
+  uint32_t cksumHead;
+  uint32_t cksumBody;
+  //char     cont[];
 } SWalHead;
 
 typedef struct {
@@ -54,16 +57,20 @@ typedef struct {
 } SWalCfg;
 
 #define WAL_PREFIX       "wal"
+#define WAL_PREFIX_LEN   3
+#define WAL_NOSUFFIX_LEN 20
+#define WAL_SUFFIX_AT    (WAL_NOSUFFIX_LEN+1)
 #define WAL_LOG_SUFFIX   "log"
 #define WAL_INDEX_SUFFIX "idx"
-#define WAL_PREFIX_LEN   3
 #define WAL_REFRESH_MS   1000
 #define WAL_MAX_SIZE     (TSDB_MAX_WAL_SIZE + sizeof(SWalHead) + 16)
 #define WAL_SIGNATURE    ((uint32_t)(0xFAFBFDFEUL))
 #define WAL_PATH_LEN     (TSDB_FILENAME_LEN + 12)
 #define WAL_FILE_LEN     (WAL_PATH_LEN + 32)
 //#define WAL_FILE_NUM     1 // 3
+#define WAL_FILESET_MAX  128
 
+#define WAL_IDX_ENTRY_SIZE     (sizeof(int64_t)*2)
 #define WAL_CUR_POS_READ_ONLY  1
 #define WAL_CUR_FILE_READ_ONLY 2
 
@@ -94,6 +101,10 @@ typedef struct SWal {
   pthread_mutex_t mutex;
   //path
   char path[WAL_PATH_LEN];
+  //file set
+  SArray* fileSet;
+  //reusable write head
+  SWalHead head;
 } SWal;  // WAL HANDLE
 
 typedef int32_t (*FWalWrite)(void *ahandle, void *pHead);
@@ -104,21 +115,20 @@ void    walCleanUp();
 
 // handle open and ctl
 SWal   *walOpen(const char *path, SWalCfg *pCfg);
-void    walStop(SWal *pWal);
 int32_t walAlter(SWal *, SWalCfg *pCfg);
 void    walClose(SWal *);
 
 // write
 //int64_t  walWriteWithMsgType(SWal*, int8_t msgType, void* body, int32_t bodyLen);
-int64_t walWrite(SWal *, int64_t index, void *body, int32_t bodyLen);
-int64_t walWriteBatch(SWal *, void **bodies, int32_t *bodyLen, int32_t batchSize);
+int64_t walWrite(SWal *, int64_t index, uint8_t msgType, void *body, int32_t bodyLen);
+//int64_t walWriteBatch(SWal *, void **bodies, int32_t *bodyLen, int32_t batchSize);
 
 // apis for lifecycle management
 void    walFsync(SWal *, bool force);
 int32_t walCommit(SWal *, int64_t ver);
 // truncate after
 int32_t walRollback(SWal *, int64_t ver);
-// notify that previous log can be pruned safely
+// notify that previous logs can be pruned safely
 int32_t walTakeSnapshot(SWal *, int64_t ver);
 //int32_t  walDataCorrupted(SWal*);
 
@@ -131,11 +141,6 @@ int64_t walGetFirstVer(SWal *);
 int64_t walGetSnapshotVer(SWal *);
 int64_t walGetLastVer(SWal *);
 
-//internal
-int32_t walGetNextFile(SWal *pWal, int64_t *nextFileId);
-int32_t walGetOldFile(SWal *pWal, int64_t curFileId, int32_t minDiff, int64_t *oldFileId);
-int32_t walGetNewFile(SWal *pWal, int64_t *newFileId);
-
 #ifdef __cplusplus
 }
 #endif
diff --git a/source/libs/wal/src/walIndex.c b/source/libs/wal/src/walIndex.c
index e1fa8c72dd..2569af841f 100644
--- a/source/libs/wal/src/walIndex.c
+++ b/source/libs/wal/src/walIndex.c
@@ -20,16 +20,42 @@
 #include "tfile.h"
 #include "walInt.h"
 
-int walSetCurVerImpl(SWal *pWal, int64_t ver) {
+int walSeekVerImpl(SWal *pWal, int64_t ver) {
   //close old file
-  //iterate all files
-  //open right file
+  int code = 0;
+  code = tfClose(pWal->curLogTfd);
+  if(code != 0) {
+   //TODO 
+  }
+  code = tfClose(pWal->curIdxTfd);
+  if(code != 0) {
+   //TODO 
+  }
+  //bsearch in fileSet
+  int fName = 0;//TODO
+  //open the right file
+  char fNameStr[WAL_FILE_LEN];
+  sprintf(fNameStr, "%d."WAL_INDEX_SUFFIX, fName);
+  bool closed = 1; //TODO:read only
+  int64_t idxTfd = tfOpenReadWrite(fNameStr);
+  sprintf(fNameStr, "%d."WAL_LOG_SUFFIX, fName);
+  int64_t logTfd = tfOpenReadWrite(fNameStr);
+  //seek position
+  int64_t offset = (ver - fName) * WAL_IDX_ENTRY_SIZE;
+  tfLseek(idxTfd, offset, SEEK_SET);
   //set cur version, cur file version and cur status
-  return 0;
+  pWal->curFileFirstVersion = fName;
+  pWal->curFileLastVersion = 1;//TODO
+  pWal->curLogTfd = logTfd;
+  pWal->curIdxTfd = idxTfd;
+  pWal->curVersion = ver;
+  pWal->curOffset = offset;
+  pWal->curStatus = 0;//TODO
+  return code;
 }
 
-int walSetCurVer(SWal *pWal, int64_t ver) {
-  if(ver > pWal->lastVersion + 1) {
+int walSeekVer(SWal *pWal, int64_t ver) {
+  if(ver > pWal->lastVersion) {
     //TODO: some records are skipped
     return -1;
   }
@@ -40,13 +66,19 @@ int walSetCurVer(SWal *pWal, int64_t ver) {
   if(ver < pWal->snapshotVersion) {
     //TODO: seek snapshotted log
   }
+  if(ver >= pWal->curFileFirstVersion
+      && ((pWal->curFileLastVersion == -1 && ver <= pWal->lastVersion) || (ver <= pWal->curFileLastVersion))) {
+
+  }
   if(ver < pWal->curFileFirstVersion || (pWal->curFileLastVersion != -1 && ver > pWal->curFileLastVersion)) {
+    int index = 0;
+    index = 1;
     //back up to avoid inconsistency
     int64_t curVersion = pWal->curVersion;
     int64_t curOffset = pWal->curOffset;
     int64_t curFileFirstVersion = pWal->curFileFirstVersion;
     int64_t curFileLastVersion = pWal->curFileLastVersion;
-    if(walSetCurVerImpl(pWal, ver) < 0) {
+    if(walSeekVerImpl(pWal, ver) < 0) {
       //TODO: errno
       pWal->curVersion = curVersion;
       pWal->curOffset = curOffset;
@@ -67,7 +99,7 @@ int walWriteIndex(SWal *pWal, int64_t ver, int64_t offset) {
     wError("vgId:%d, file:%"PRId64".idx, failed to open since %s", pWal->vgId, pWal->curFileFirstVersion, strerror(errno));
   }
   if(pWal->curVersion != ver) {
-    if(walSetCurVer(pWal, ver) != 0) {
+    if(walSeekVer(pWal, ver) != 0) {
       //TODO: some records are skipped
       return -1;
     }
diff --git a/source/libs/wal/src/walMgmt.c b/source/libs/wal/src/walMgmt.c
index 83f9c3b04e..d60cdfe118 100644
--- a/source/libs/wal/src/walMgmt.c
+++ b/source/libs/wal/src/walMgmt.c
@@ -18,8 +18,17 @@
 #include "taoserror.h"
 #include "tref.h"
 #include "tfile.h"
+#include "compare.h"
 #include "walInt.h"
 
+//internal
+int32_t walGetNextFile(SWal *pWal, int64_t *nextFileId);
+int32_t walGetOldFile(SWal *pWal, int64_t curFileId, int32_t minDiff, int64_t *oldFileId);
+int32_t walGetNewFile(SWal *pWal, int64_t *newFileId);
+
+static pthread_mutex_t walInitLock = PTHREAD_MUTEX_INITIALIZER;
+static int8_t walInited = 0;
+
 typedef struct {
   int32_t   refSetId;
   int32_t   seq;
@@ -35,11 +44,21 @@ static int32_t  walInitObj(SWal *pWal);
 static void     walFreeObj(void *pWal);
 
 int32_t walInit() {
+  //TODO: change to atomic
+  pthread_mutex_lock(&walInitLock);
+  if(walInited) {
+    pthread_mutex_unlock(&walInitLock);
+    return 0;
+  } else {
+    walInited = 1;
+    pthread_mutex_unlock(&walInitLock);
+  }
+
   int32_t code = 0;
   tsWal.refSetId = taosOpenRef(TSDB_MIN_VNODES, walFreeObj);
 
   code = pthread_mutex_init(&tsWal.mutex, NULL);
-  if (code) {
+  if (code != 0) {
     wError("failed to init wal mutex since %s", tstrerror(code));
     return code;
   }
@@ -61,6 +80,27 @@ void walCleanUp() {
   wInfo("wal module is cleaned up");
 }
 
+static int walLoadFileset(SWal *pWal) {
+  DIR *dir = opendir(pWal->path);
+  if (dir == NULL) {
+    wError("vgId:%d, path:%s, failed to open since %s", pWal->vgId, pWal->path, strerror(errno));
+    return -1;
+  }
+
+  struct dirent* ent;
+  while ((ent = readdir(dir)) != NULL) {
+    char *name = ent->d_name;
+    name[WAL_NOSUFFIX_LEN] = 0;
+    //validate file name by regex matching
+    if(1 /* regex match */) {
+      int64_t fnameInt64 = atoll(name);
+      taosArrayPush(pWal->fileSet, &fnameInt64);
+    }
+  }
+  taosArraySort(pWal->fileSet, compareInt64Val);
+  return 0;
+}
+
 SWal *walOpen(const char *path, SWalCfg *pCfg) {
   SWal *pWal = malloc(sizeof(SWal));
   if (pWal == NULL) {
@@ -70,9 +110,13 @@ SWal *walOpen(const char *path, SWalCfg *pCfg) {
 
   pWal->vgId = pCfg->vgId;
   pWal->curLogTfd = -1;
-  /*pWal->curFileId = -1;*/
+  pWal->curIdxTfd = -1;
   pWal->level = pCfg->walLevel;
   pWal->fsyncPeriod = pCfg->fsyncPeriod;
+
+  memset(&pWal->head, 0, sizeof(SWalHead));
+  pWal->head.sver = 0;
+
   tstrncpy(pWal->path, path, sizeof(pWal->path));
   pthread_mutex_init(&pWal->mutex, NULL);
 
@@ -129,6 +173,11 @@ static int32_t walInitObj(SWal *pWal) {
     wError("vgId:%d, path:%s, failed to create directory since %s", pWal->vgId, pWal->path, strerror(errno));
     return TAOS_SYSTEM_ERROR(errno);
   }
+  pWal->fileSet = taosArrayInit(0, sizeof(int64_t));
+  if(pWal->fileSet == NULL) {
+    wError("vgId:%d, path:%s, failed to init taosArray %s", pWal->vgId, pWal->path, strerror(errno));
+    return TAOS_SYSTEM_ERROR(errno);
+  }
 
   wDebug("vgId:%d, object is initialized", pWal->vgId);
   return 0;
diff --git a/source/libs/wal/src/wal.c b/source/libs/wal/src/walRead.c
similarity index 65%
rename from source/libs/wal/src/wal.c
rename to source/libs/wal/src/walRead.c
index 59f9c48814..b475183b7b 100644
--- a/source/libs/wal/src/wal.c
+++ b/source/libs/wal/src/walRead.c
@@ -14,18 +14,13 @@
  */
 
 #include "wal.h"
+#include "tchecksum.h"
 
-int32_t walCommit(SWal *pWal, int64_t ver) {
-  return 0;
+static int walValidateChecksum(SWalHead *pHead, void* body, int64_t bodyLen) {
+  return taosCheckChecksum((uint8_t*)pHead, sizeof(SWalHead) - sizeof(uint32_t)*2, pHead->cksumHead) &&
+    taosCheckChecksum(body, bodyLen, pHead->cksumBody);
 }
 
-int32_t walRollback(SWal *pWal, int64_t ver) {
-  return 0;
-}
-
-int32_t walTakeSnapshot(SWal *pWal, int64_t ver) {
-  return 0;
-}
 
 int32_t walRead(SWal *pWal, SWalHead **ppHead, int64_t ver) {
   return 0;
@@ -36,13 +31,16 @@ int32_t walReadWithFp(SWal *pWal, FWalWrite writeFp, int64_t verStart, int32_t r
 }
 
 int64_t walGetFirstVer(SWal *pWal) {
-  return 0;
+  if (pWal == NULL) return 0;
+  return pWal->firstVersion;
 }
 
-int64_t walGetSnapshotVer(SWal *pWal) {
-  return 0;
+int64_t walGetSnaphostVer(SWal *pWal) {
+  if (pWal == NULL) return 0;
+  return pWal->snapshotVersion;
 }
 
 int64_t walGetLastVer(SWal *pWal) {
-  return 0;
+  if (pWal == NULL) return 0;
+  return pWal->lastVersion;
 }
diff --git a/source/libs/wal/src/walWrite.c b/source/libs/wal/src/walWrite.c
index a8123f9c25..7563ec02c7 100644
--- a/source/libs/wal/src/walWrite.c
+++ b/source/libs/wal/src/walWrite.c
@@ -21,6 +21,18 @@
 #include "tfile.h"
 #include "walInt.h"
 
+int32_t walCommit(SWal *pWal, int64_t ver) {
+  return 0;
+}
+
+int32_t walRollback(SWal *pWal, int64_t ver) {
+  return 0;
+}
+
+int32_t walTakeSnapshot(SWal *pWal, int64_t ver) {
+  return 0;
+}
+
 #if 0
 static int32_t walRestoreWalFile(SWal *pWal, void *pVnode, FWalWrite writeFp, char *name, int64_t fileId);
 
@@ -112,60 +124,40 @@ void walRemoveAllOldFiles(void *handle) {
 }
 #endif
 
-static void walUpdateChecksum(SWalHead *pHead) {
-  pHead->sver = 2;
-  pHead->cksum = taosCalcChecksum(0, (uint8_t *)pHead, sizeof(SWalHead) + pHead->len);
-}
-
-static int walValidateChecksum(SWalHead *pHead) {
-  if (pHead->sver == 0) { // for compatible with wal before sver 1
-    return taosCheckChecksumWhole((uint8_t *)pHead, sizeof(*pHead));
-  } else if (pHead->sver >= 1) {
-    uint32_t cksum = pHead->cksum;
-    pHead->cksum = 0;
-    return taosCheckChecksum((uint8_t *)pHead, sizeof(*pHead) + pHead->len, cksum);
-  }
-
-  return 0;
-}
-
-int64_t walWrite(SWal *pWal, int64_t index, void *body, int32_t bodyLen) {
+int64_t walWrite(SWal *pWal, int64_t index, uint8_t msgType, void *body, int32_t bodyLen) {
   if (pWal == NULL) return -1;
 
-  SWalHead *pHead = malloc(sizeof(SWalHead) + bodyLen);
-  if(pHead == NULL) {
-    return -1;
-  }
-  pHead->version = index;
-  int32_t code = 0;
-
   // no wal
   if (!tfValid(pWal->curLogTfd)) return 0;
   if (pWal->level == TAOS_WAL_NOLOG) return 0;
-  if (pHead->version <= pWal->curVersion) return 0;
+  if (index > pWal->lastVersion + 1) return -1;
 
-  pHead->signature = WAL_SIGNATURE;
-  pHead->len = bodyLen;
-  memcpy(pHead->cont, body, bodyLen);
+  pWal->head.version = index;
+  int32_t code = 0;
 
-  walUpdateChecksum(pHead);
+  pWal->head.signature = WAL_SIGNATURE;
+  pWal->head.len = bodyLen;
+  pWal->head.msgType = msgType;
 
-  int32_t contLen = pHead->len + sizeof(SWalHead);
+  pWal->head.cksumHead = taosCalcChecksum(0, (const uint8_t*)&pWal->head, sizeof(SWalHead)- sizeof(uint32_t)*2);
+  pWal->head.cksumBody = taosCalcChecksum(0, (const uint8_t*)&body, bodyLen);
 
   pthread_mutex_lock(&pWal->mutex);
 
-  if (tfWrite(pWal->curLogTfd, pHead, contLen) != contLen) {
+  if (tfWrite(pWal->curLogTfd, &pWal->head, sizeof(SWalHead)) != sizeof(SWalHead)) {
+    //ftruncate
     code = TAOS_SYSTEM_ERROR(errno);
     wError("vgId:%d, file:%"PRId64".log, failed to write since %s", pWal->vgId, pWal->curFileFirstVersion, strerror(errno));
-  } else {
-    /*wTrace("vgId:%d, write wal, fileId:%" PRId64 " tfd:%" PRId64 " hver:%" PRId64 " wver:%" PRIu64 " len:%d", pWal->vgId,*/
-           /*pWal->curFileId, pWal->logTfd, pHead->version, pWal->curVersion, pHead->len);*/
-    pWal->curVersion = pHead->version;
   }
 
-  pthread_mutex_unlock(&pWal->mutex);
+  if (tfWrite(pWal->curLogTfd, &body, bodyLen) != bodyLen) {
+    //ftruncate
+    code = TAOS_SYSTEM_ERROR(errno);
+    wError("vgId:%d, file:%"PRId64".log, failed to write since %s", pWal->vgId, pWal->curFileFirstVersion, strerror(errno));
+  }
+  //TODO:write idx
 
-  ASSERT(contLen == pHead->len + sizeof(SWalHead));
+  pthread_mutex_unlock(&pWal->mutex);
 
   return code;
 }
@@ -254,6 +246,7 @@ static void walFtruncate(SWal *pWal, int64_t tfd, int64_t offset) {
   tfFsync(tfd);
 }
 
+#if 0
 static int32_t walSkipCorruptedRecord(SWal *pWal, SWalHead *pHead, int64_t tfd, int64_t *offset) {
   int64_t pos = *offset;
   while (1) {
@@ -387,21 +380,4 @@ static int32_t walRestoreWalFile(SWal *pWal, void *pVnode, FWalWrite writeFp, ch
   wDebug("vgId:%d, file:%s, it is closed after restore", pWal->vgId, name);
   return code;
 }
-
-uint64_t walGetVersion(SWal *pWal) {
-  if (pWal == NULL) return 0;
-
-  return pWal->curVersion;
-}
-
-// Wal version in slave (dnode1) must be reset. 
-// Because after the data file is recovered from peer (dnode2), the new file version in dnode1 may become smaller than origin.
-// Some new wal record cannot be written to the wal file in dnode1 for wal version not reset, then fversion and the record in wal file may inconsistent, 
-// At this time, if dnode2 down, dnode1 switched to master. After dnode2 start and restore data from dnode1, data loss will occur
-
-void walResetVersion(SWal *pWal, uint64_t newVer) {
-  if (pWal == NULL) return;
-  wInfo("vgId:%d, version reset from %" PRIu64 " to %" PRIu64, pWal->vgId, pWal->curVersion, newVer);
-
-  pWal->curVersion = newVer;
-}
+#endif