diff --git a/src/meta/processors/admin/AdminClient.cpp b/src/meta/processors/admin/AdminClient.cpp
index 3decaf0b314..f238a728d50 100644
--- a/src/meta/processors/admin/AdminClient.cpp
+++ b/src/meta/processors/admin/AdminClient.cpp
@@ -28,7 +28,7 @@ folly::Future<Status> AdminClient::transLeader(GraphSpaceID spaceId,
   req.part_id_ref() = partId;
   auto ret = getPeers(spaceId, partId);
   if (!nebula::ok(ret)) {
-    LOG(ERROR) << "Get peers failed: " << static_cast<int32_t>(nebula::error(ret));
+    LOG(INFO) << "Get peers failed: " << static_cast<int32_t>(nebula::error(ret));
     return Status::Error("Get peers failed");
   }
 
@@ -83,7 +83,7 @@ folly::Future<Status> AdminClient::addPart(GraphSpaceID spaceId,
   req.as_learner_ref() = asLearner;
   auto ret = getPeers(spaceId, partId);
   if (!nebula::ok(ret)) {
-    LOG(ERROR) << "Get peers failed: " << static_cast<int32_t>(nebula::error(ret));
+    LOG(INFO) << "Get peers failed: " << static_cast<int32_t>(nebula::error(ret));
     return Status::Error("Get peers failed");
   }
 
@@ -110,7 +110,7 @@ folly::Future<Status> AdminClient::addLearner(GraphSpaceID spaceId,
   req.learner_ref() = learner;
   auto ret = getPeers(spaceId, partId);
   if (!nebula::ok(ret)) {
-    LOG(ERROR) << "Get peers failed: " << static_cast<int32_t>(nebula::error(ret));
+    LOG(INFO) << "Get peers failed: " << static_cast<int32_t>(nebula::error(ret));
     return Status::Error("Get peers failed");
   }
 
@@ -137,7 +137,7 @@ folly::Future<Status> AdminClient::waitingForCatchUpData(GraphSpaceID spaceId,
   req.target_ref() = target;
   auto ret = getPeers(spaceId, partId);
   if (!nebula::ok(ret)) {
-    LOG(ERROR) << "Get peers failed: " << static_cast<int32_t>(nebula::error(ret));
+    LOG(INFO) << "Get peers failed: " << static_cast<int32_t>(nebula::error(ret));
     return Status::Error("Get peers failed");
   }
 
@@ -166,7 +166,7 @@ folly::Future<Status> AdminClient::memberChange(GraphSpaceID spaceId,
   req.peer_ref() = peer;
   auto ret = getPeers(spaceId, partId);
   if (!nebula::ok(ret)) {
-    LOG(ERROR) << "Get peers failed: " << static_cast<int32_t>(nebula::error(ret));
+    LOG(INFO) << "Get peers failed: " << static_cast<int32_t>(nebula::error(ret));
     return Status::Error("Get peers failed");
   }
 
@@ -191,7 +191,7 @@ folly::Future<Status> AdminClient::updateMeta(GraphSpaceID spaceId,
   CHECK_NOTNULL(kv_);
   auto ret = getPeers(spaceId, partId);
   if (!nebula::ok(ret)) {
-    LOG(ERROR) << "Get peers failed: " << static_cast<int32_t>(nebula::error(ret));
+    LOG(INFO) << "Get peers failed: " << static_cast<int32_t>(nebula::error(ret));
     return Status::Error("Get peers failed");
   }
 
@@ -267,7 +267,7 @@ folly::Future<Status> AdminClient::checkPeers(GraphSpaceID spaceId, PartitionID
   req.part_id_ref() = partId;
   auto peerRet = getPeers(spaceId, partId);
   if (!nebula::ok(peerRet)) {
-    LOG(ERROR) << "Get peers failed: " << static_cast<int32_t>(nebula::error(peerRet));
+    LOG(INFO) << "Get peers failed: " << static_cast<int32_t>(nebula::error(peerRet));
     return Status::Error("Get peers failed");
   }
 
@@ -554,8 +554,8 @@ void AdminClient::getLeaderDist(const HostAddr& host,
         .then([pro = std::move(pro), host, retry, retryLimit, this](
                   folly::Try<storage::cpp2::GetLeaderPartsResp>&& t) mutable {
           if (t.hasException()) {
-            LOG(ERROR) << folly::stringPrintf("RPC failure in AdminClient: %s",
-                                              t.exception().what().c_str());
+            LOG(INFO) << folly::stringPrintf("RPC failure in AdminClient: %s",
+                                             t.exception().what().c_str());
             if (retry < retryLimit) {
               usleep(1000 * 50);
               getLeaderDist(
@@ -637,8 +637,8 @@ folly::Future<StatusOr<cpp2::HostBackupInfo>> AdminClient::createSnapshot(
         .then([p = std::move(pro), storageHost, host](
                   folly::Try<storage::cpp2::CreateCPResp>&& t) mutable {
           if (t.hasException()) {
-            LOG(ERROR) << folly::stringPrintf("RPC failure in AdminClient: %s",
-                                              t.exception().what().c_str());
+            LOG(INFO) << folly::stringPrintf("RPC failure in AdminClient: %s",
+                                             t.exception().what().c_str());
             p.setValue(Status::Error("RPC failure in createCheckpoint"));
             return;
           }
diff --git a/src/meta/processors/admin/AdminClient.h b/src/meta/processors/admin/AdminClient.h
index 88527c5c54c..cb3ffbdc982 100644
--- a/src/meta/processors/admin/AdminClient.h
+++ b/src/meta/processors/admin/AdminClient.h
@@ -43,57 +43,168 @@ class AdminClient {
     return ioThreadPool_.get();
   }
 
+  /**
+   * @brief Transfer given partition's leader from now to dst
+   *
+   * @param spaceId
+   * @param partId
+   * @param leader
+   * @param dst
+   * @return folly::Future<Status>
+   */
   virtual folly::Future<Status> transLeader(GraphSpaceID spaceId,
                                             PartitionID partId,
                                             const HostAddr& leader,
                                             const HostAddr& dst = kRandomPeer);
 
+  /**
+   * @brief Add a peer for given partition in specified host. The rpc
+   *        will be sent to the new partition peer, letting it know the
+   *        other peers.
+   *
+   * @param spaceId
+   * @param partId
+   * @param host
+   * @param asLearner Add an peer only as raft learner
+   * @return folly::Future<Status>
+   */
   virtual folly::Future<Status> addPart(GraphSpaceID spaceId,
                                         PartitionID partId,
                                         const HostAddr& host,
                                         bool asLearner);
 
+  /**
+   * @brief Add a learner for given partition. The rpc will be sent to
+   *        the partition leader, writting the add event as a log.
+   *
+   * @param spaceId
+   * @param partId
+   * @param learner
+   * @return folly::Future<Status>
+   */
   virtual folly::Future<Status> addLearner(GraphSpaceID spaceId,
                                            PartitionID partId,
                                            const HostAddr& learner);
 
+  /**
+   * @brief Waiting for give partition peer catching data
+   *
+   * @param spaceId
+   * @param partId
+   * @param target partition peer address
+   * @return folly::Future<Status>
+   */
   virtual folly::Future<Status> waitingForCatchUpData(GraphSpaceID spaceId,
                                                       PartitionID partId,
                                                       const HostAddr& target);
 
   /**
-   * Add/Remove one peer for raft group (spaceId, partId).
-   * "added" should be true if we want to add one peer, otherwise it is false.
-   * */
+   * @brief Add/Remove one peer for partition (spaceId, partId).
+   *        "added" should be true if we want to add one peer, otherwise it is false.
+   * @param spaceId
+   * @param partId
+   * @param peer
+   * @param added
+   * @return folly::Future<Status>
+   */
   virtual folly::Future<Status> memberChange(GraphSpaceID spaceId,
                                              PartitionID partId,
                                              const HostAddr& peer,
                                              bool added);
 
+  /**
+   * @brief Update partition peers info in meta kvstore, remove peer 'src', add peer 'dst'
+   *
+   * @param spaceId
+   * @param partId
+   * @param src
+   * @param dst
+   * @return folly::Future<Status>
+   */
   virtual folly::Future<Status> updateMeta(GraphSpaceID spaceId,
                                            PartitionID partId,
-                                           const HostAddr& leader,
+                                           const HostAddr& src,
                                            const HostAddr& dst);
 
+  /**
+   * @brief Remove partition peer in given storage host
+   *
+   * @param spaceId
+   * @param partId
+   * @param host storage admin service address
+   * @return folly::Future<Status>
+   */
   virtual folly::Future<Status> removePart(GraphSpaceID spaceId,
                                            PartitionID partId,
                                            const HostAddr& host);
 
+  /**
+   * @brief Check and adjust(add/remove) each peer's peers info according to meta kv store
+   *
+   * @param spaceId
+   * @param partId
+   * @return folly::Future<Status>
+   */
   virtual folly::Future<Status> checkPeers(GraphSpaceID spaceId, PartitionID partId);
 
+  /**
+   * @brief Get the all partitions' leader distribution
+   *
+   * @param result
+   * @return folly::Future<Status>
+   */
   virtual folly::Future<Status> getLeaderDist(HostLeaderMap* result);
 
+  // used for snapshot and backup
+  /**
+   * @brief Create snapshots for given spaces in given host with specified snapshot name
+   *
+   * @param spaceIds spaces to create snapshot
+   * @param name snapshot name
+   * @param host storage host
+   * @return folly::Future<StatusOr<cpp2::HostBackupInfo>>
+   */
   virtual folly::Future<StatusOr<cpp2::HostBackupInfo>> createSnapshot(
       const std::set<GraphSpaceID>& spaceIds, const std::string& name, const HostAddr& host);
 
+  /**
+   * @brief Drop snapshots of given spaces in given host with specified snapshot name
+   *
+   * @param spaceIds spaces to drop
+   * @param name snapshot name
+   * @param host storage host
+   * @return folly::Future<Status>
+   */
   virtual folly::Future<Status> dropSnapshot(const std::set<GraphSpaceID>& spaceIds,
                                              const std::string& name,
                                              const HostAddr& host);
 
+  /**
+   * @brief Blocking/Allowing writings to given spaces in specified storage host
+   *
+   * @param spaceIds
+   * @param sign BLOCK_ON: blocking, BLOCK_OFF: allowing
+   * @param host
+   * @return folly::Future<Status>
+   */
   virtual folly::Future<Status> blockingWrites(const std::set<GraphSpaceID>& spaceIds,
                                                storage::cpp2::EngineSignType sign,
                                                const HostAddr& host);
 
+  /**
+   * @brief Add storage admin task to given storage host
+   *
+   * @param cmd
+   * @param jobId
+   * @param taskId
+   * @param spaceId
+   * @param specificHosts if hosts are empty, will send request to all ative storage hosts
+   * @param taskSpecficParas
+   * @param parts
+   * @param concurrency
+   * @param statsResult
+   * @return folly::Future<Status>
+   */
   virtual folly::Future<Status> addTask(cpp2::AdminCmd cmd,
                                         int32_t jobId,
                                         int32_t taskId,
@@ -104,6 +215,14 @@ class AdminClient {
                                         int concurrency,
                                         cpp2::StatsItem* statsResult = nullptr);
 
+  /**
+   * @brief Stop stoarge admin task in given storage host
+   *
+   * @param target if target hosts are emtpy, will send request to all active storage hosts
+   * @param jobId
+   * @param taskId
+   * @return folly::Future<Status>
+   */
   virtual folly::Future<Status> stopTask(const std::vector<HostAddr>& target,
                                          int32_t jobId,
                                          int32_t taskId);
diff --git a/src/meta/processors/admin/AgentHBProcessor.cpp b/src/meta/processors/admin/AgentHBProcessor.cpp
index 1df56fdab0e..8f6b42181d4 100644
--- a/src/meta/processors/admin/AgentHBProcessor.cpp
+++ b/src/meta/processors/admin/AgentHBProcessor.cpp
@@ -24,7 +24,6 @@ void AgentHBProcessor::onFinished() {
   Base::onFinished();
 }
 
-// Agent heartbeat register agent to meta and pull all services info in agent's host
 void AgentHBProcessor::process(const cpp2::AgentHBReq& req) {
   HostAddr agentAddr((*req.host_ref()).host, (*req.host_ref()).port);
   LOG(INFO) << "Receive heartbeat from " << agentAddr << ", role = AGENT";
@@ -36,9 +35,9 @@ void AgentHBProcessor::process(const cpp2::AgentHBReq& req) {
         time::WallClock::fastNowInMilliSec(), cpp2::HostRole::AGENT, req.get_git_info_sha());
     ret = ActiveHostsMan::updateHostInfo(kvstore_, agentAddr, info);
     if (ret != nebula::cpp2::ErrorCode::SUCCEEDED) {
-      LOG(ERROR) << folly::sformat("Put agent {} info failed: {}",
-                                   agentAddr.toString(),
-                                   apache::thrift::util::enumNameSafe(ret));
+      LOG(INFO) << folly::sformat("Put agent {} info failed: {}",
+                                  agentAddr.toString(),
+                                  apache::thrift::util::enumNameSafe(ret));
       break;
     }
 
@@ -46,9 +45,9 @@ void AgentHBProcessor::process(const cpp2::AgentHBReq& req) {
     auto servicesRet = ActiveHostsMan::getServicesInHost(kvstore_, agentAddr.host);
     if (!nebula::ok(servicesRet)) {
       ret = nebula::error(servicesRet);
-      LOG(ERROR) << folly::sformat("Get active services for {} failed: {}",
-                                   agentAddr.host,
-                                   apache::thrift::util::enumNameSafe(ret));
+      LOG(INFO) << folly::sformat("Get active services for {} failed: {}",
+                                  agentAddr.host,
+                                  apache::thrift::util::enumNameSafe(ret));
       break;
     }
 
@@ -58,9 +57,9 @@ void AgentHBProcessor::process(const cpp2::AgentHBReq& req) {
     auto dirIterRet = doPrefix(hostDirHostPrefix);
     if (!nebula::ok(dirIterRet)) {
       ret = nebula::error(dirIterRet);
-      LOG(ERROR) << folly::sformat("Get host {} dir prefix iterator failed: {}",
-                                   agentAddr.host,
-                                   apache::thrift::util::enumNameSafe(ret));
+      LOG(INFO) << folly::sformat("Get host {} dir prefix iterator failed: {}",
+                                  agentAddr.host,
+                                  apache::thrift::util::enumNameSafe(ret));
       break;
     }
     auto dirIter = std::move(nebula::value(dirIterRet));
@@ -86,7 +85,7 @@ void AgentHBProcessor::process(const cpp2::AgentHBReq& req) {
 
       auto it = serviceDirinfo.find(addr);
       if (it == serviceDirinfo.end()) {
-        LOG(ERROR) << folly::sformat("{} dir info not found", addr.toString());
+        LOG(INFO) << folly::sformat("{} dir info not found", addr.toString());
         break;
       }
 
@@ -99,7 +98,7 @@ void AgentHBProcessor::process(const cpp2::AgentHBReq& req) {
     if (serviceList.size() != services.size() - 1) {
       ret = nebula::cpp2::ErrorCode::E_AGENT_HB_FAILUE;
       // missing some services' dir info
-      LOG(ERROR) << folly::sformat(
+      LOG(INFO) << folly::sformat(
           "Missing some services's dir info, excepted service {}, but only got {}",
           services.size() - 1,
           serviceList.size());
@@ -111,8 +110,7 @@ void AgentHBProcessor::process(const cpp2::AgentHBReq& req) {
     auto partRet = kvstore_->part(kDefaultSpaceId, kDefaultPartId);
     if (!nebula::ok(partRet)) {
       ret = nebula::error(partRet);
-      LOG(ERROR) << "Get meta part store failed, error: "
-                 << apache::thrift::util::enumNameSafe(ret);
+      LOG(INFO) << "Get meta part store failed, error: " << apache::thrift::util::enumNameSafe(ret);
       return;
     }
     auto raftPeers = nebula::value(partRet)->peers();
diff --git a/src/meta/processors/admin/AgentHBProcessor.h b/src/meta/processors/admin/AgentHBProcessor.h
index 0119bb730fb..9591c631b7b 100644
--- a/src/meta/processors/admin/AgentHBProcessor.h
+++ b/src/meta/processors/admin/AgentHBProcessor.h
@@ -30,6 +30,9 @@ struct AgentHBCounters final {
 };
 extern AgentHBCounters kAgentHBCounters;
 
+/**
+ * @brief Agent heartbeat register agent to meta and pull all services info in agent's host
+ */
 class AgentHBProcessor : public BaseProcessor<cpp2::AgentHBResp> {
   FRIEND_TEST(AgentHBProcessorTest, AgentHBTest);
 
diff --git a/src/meta/processors/admin/CreateBackupProcessor.cpp b/src/meta/processors/admin/CreateBackupProcessor.cpp
index 709a6ebfa08..85d74c7001d 100644
--- a/src/meta/processors/admin/CreateBackupProcessor.cpp
+++ b/src/meta/processors/admin/CreateBackupProcessor.cpp
@@ -30,7 +30,7 @@ CreateBackupProcessor::spaceNameToId(const std::vector<std::string>* backupSpace
     auto result = doMultiGet(std::move(keys));
     if (!nebula::ok(result)) {
       auto err = nebula::error(result);
-      LOG(ERROR) << "Failed to get space id, error: " << apache::thrift::util::enumNameSafe(err);
+      LOG(INFO) << "Failed to get space id, error: " << apache::thrift::util::enumNameSafe(err);
       if (err == nebula::cpp2::ErrorCode::E_KEY_NOT_FOUND) {
         return nebula::cpp2::ErrorCode::E_BACKUP_SPACE_NOT_FOUND;
       }
@@ -50,7 +50,7 @@ CreateBackupProcessor::spaceNameToId(const std::vector<std::string>* backupSpace
     auto iterRet = doPrefix(prefix);
     if (!nebula::ok(iterRet)) {
       auto retCode = nebula::error(iterRet);
-      LOG(ERROR) << "Space prefix failed, error: " << apache::thrift::util::enumNameSafe(retCode);
+      LOG(INFO) << "Space prefix failed, error: " << apache::thrift::util::enumNameSafe(retCode);
       return retCode;
     }
 
@@ -65,8 +65,8 @@ CreateBackupProcessor::spaceNameToId(const std::vector<std::string>* backupSpace
   }
 
   if (spaces.empty()) {
-    LOG(ERROR) << "Failed to create a full backup because there is currently "
-                  "no space.";
+    LOG(INFO) << "Failed to create a full backup because there is currently "
+                 "no space.";
     return nebula::cpp2::ErrorCode::E_BACKUP_SPACE_NOT_FOUND;
   }
 
@@ -86,13 +86,13 @@ void CreateBackupProcessor::process(const cpp2::CreateBackupReq& req) {
   // make sure there is no index job
   auto result = jobMgr->checkIndexJobRunning();
   if (!nebula::ok(result)) {
-    LOG(ERROR) << "get Index status failed, not allowed to create backup.";
+    LOG(INFO) << "Get Index status failed, not allowed to create backup.";
     handleErrorCode(nebula::error(result));
     onFinished();
     return;
   }
   if (nebula::value(result)) {
-    LOG(ERROR) << "Index is rebuilding, not allowed to create backup.";
+    LOG(INFO) << "Index is rebuilding, not allowed to create backup.";
     handleErrorCode(nebula::cpp2::ErrorCode::E_BACKUP_BUILDING_INDEX);
     onFinished();
     return;
@@ -109,7 +109,7 @@ void CreateBackupProcessor::process(const cpp2::CreateBackupReq& req) {
   }
   auto hosts = std::move(nebula::value(activeHostsRet));
   if (hosts.empty()) {
-    LOG(ERROR) << "There has some offline hosts";
+    LOG(INFO) << "There are some offline hosts";
     handleErrorCode(nebula::cpp2::ErrorCode::E_NO_HOSTS);
     onFinished();
     return;
@@ -133,7 +133,7 @@ void CreateBackupProcessor::process(const cpp2::CreateBackupReq& req) {
       MetaKeyUtils::snapshotVal(cpp2::SnapshotStatus::INVALID, NetworkUtils::toHostsStr(hosts)));
   auto putRet = doSyncPut(data);
   if (putRet != nebula::cpp2::ErrorCode::SUCCEEDED) {
-    LOG(ERROR) << "Write backup meta error";
+    LOG(INFO) << "Write backup meta error";
     handleErrorCode(putRet);
     onFinished();
     return;
@@ -143,11 +143,11 @@ void CreateBackupProcessor::process(const cpp2::CreateBackupReq& req) {
   // step 2 : Blocking all writes action for storage engines.
   auto ret = Snapshot::instance(kvstore_, client_)->blockingWrites(SignType::BLOCK_ON);
   if (ret != nebula::cpp2::ErrorCode::SUCCEEDED) {
-    LOG(ERROR) << "Send blocking sign to storage engine error";
+    LOG(INFO) << "Send blocking sign to storage engine error";
     handleErrorCode(ret);
     ret = Snapshot::instance(kvstore_, client_)->blockingWrites(SignType::BLOCK_OFF);
     if (ret != nebula::cpp2::ErrorCode::SUCCEEDED) {
-      LOG(ERROR) << "Cancel write blocking error";
+      LOG(INFO) << "Cancel write blocking error";
     }
     onFinished();
     return;
@@ -156,12 +156,12 @@ void CreateBackupProcessor::process(const cpp2::CreateBackupReq& req) {
   // step 3 : Create checkpoint for all storage engines.
   auto sret = Snapshot::instance(kvstore_, client_)->createSnapshot(backupName);
   if (!nebula::ok(sret)) {
-    LOG(ERROR) << "Checkpoint create error on storage engine: "
-               << apache::thrift::util::enumNameSafe(nebula::error(sret));
+    LOG(INFO) << "Checkpoint create error on storage engine: "
+              << apache::thrift::util::enumNameSafe(nebula::error(sret));
     handleErrorCode(nebula::error(sret));
     ret = Snapshot::instance(kvstore_, client_)->blockingWrites(SignType::BLOCK_OFF);
     if (ret != nebula::cpp2::ErrorCode::SUCCEEDED) {
-      LOG(ERROR) << "Cancel write blocking error";
+      LOG(INFO) << "Cancel write blocking error";
     }
     onFinished();
     return;
@@ -170,7 +170,7 @@ void CreateBackupProcessor::process(const cpp2::CreateBackupReq& req) {
   // step 4 created backup for meta(export sst).
   auto backupFiles = MetaServiceUtils::backupTables(kvstore_, spaces, backupName, backupSpaces);
   if (!nebula::ok(backupFiles)) {
-    LOG(ERROR) << "Failed backup meta";
+    LOG(INFO) << "Failed backup meta";
     handleErrorCode(nebula::cpp2::ErrorCode::E_BACKUP_FAILED);
     onFinished();
     return;
@@ -179,7 +179,7 @@ void CreateBackupProcessor::process(const cpp2::CreateBackupReq& req) {
   // step 5 : checkpoint created done, so release the write blocking.
   ret = Snapshot::instance(kvstore_, client_)->blockingWrites(SignType::BLOCK_OFF);
   if (ret != nebula::cpp2::ErrorCode::SUCCEEDED) {
-    LOG(ERROR) << "Cancel write blocking error";
+    LOG(INFO) << "Cancel write blocking error";
     handleErrorCode(ret);
     onFinished();
     return;
@@ -192,10 +192,10 @@ void CreateBackupProcessor::process(const cpp2::CreateBackupReq& req) {
       MetaKeyUtils::snapshotVal(cpp2::SnapshotStatus::VALID, NetworkUtils::toHostsStr(hosts)));
   putRet = doSyncPut(std::move(data));
   if (putRet != nebula::cpp2::ErrorCode::SUCCEEDED) {
-    LOG(ERROR) << "All checkpoint creations are done, "
-                  "but update checkpoint status error. "
-                  "backup : "
-               << backupName;
+    LOG(INFO) << "All checkpoint creations are done, "
+                 "but update checkpoint status error. "
+                 "backup : "
+              << backupName;
     handleErrorCode(putRet);
     onFinished();
     return;
diff --git a/src/meta/processors/admin/CreateBackupProcessor.h b/src/meta/processors/admin/CreateBackupProcessor.h
index a5df484109e..df75ac036ef 100644
--- a/src/meta/processors/admin/CreateBackupProcessor.h
+++ b/src/meta/processors/admin/CreateBackupProcessor.h
@@ -14,6 +14,10 @@
 namespace nebula {
 namespace meta {
 
+/**
+ * @brief Create backup files in each mtead and storaged services' local.
+ *
+ */
 class CreateBackupProcessor : public BaseProcessor<cpp2::CreateBackupResp> {
  public:
   static CreateBackupProcessor* instance(kvstore::KVStore* kvstore, AdminClient* client) {
diff --git a/src/meta/processors/admin/CreateSnapshotProcessor.cpp b/src/meta/processors/admin/CreateSnapshotProcessor.cpp
index 1b50904cbb1..d38ae92a688 100644
--- a/src/meta/processors/admin/CreateSnapshotProcessor.cpp
+++ b/src/meta/processors/admin/CreateSnapshotProcessor.cpp
@@ -24,7 +24,7 @@ void CreateSnapshotProcessor::process(const cpp2::CreateSnapshotReq&) {
   }
 
   if (nebula::value(result)) {
-    LOG(ERROR) << "Index is rebuilding, not allowed to create snapshot.";
+    LOG(INFO) << "Index is rebuilding, not allowed to create snapshot.";
     handleErrorCode(nebula::cpp2::ErrorCode::E_SNAPSHOT_FAILURE);
     onFinished();
     return;
@@ -42,7 +42,7 @@ void CreateSnapshotProcessor::process(const cpp2::CreateSnapshotReq&) {
   auto hosts = std::move(nebula::value(activeHostsRet));
 
   if (hosts.empty()) {
-    LOG(ERROR) << "There is no active hosts";
+    LOG(INFO) << "There is no active hosts";
     handleErrorCode(nebula::cpp2::ErrorCode::E_NO_HOSTS);
     onFinished();
     return;
@@ -58,7 +58,7 @@ void CreateSnapshotProcessor::process(const cpp2::CreateSnapshotReq&) {
 
   auto putRet = doSyncPut(std::move(data));
   if (putRet != nebula::cpp2::ErrorCode::SUCCEEDED) {
-    LOG(ERROR) << "Write snapshot meta error";
+    LOG(INFO) << "Write snapshot meta error";
     handleErrorCode(putRet);
     onFinished();
     return;
@@ -67,7 +67,7 @@ void CreateSnapshotProcessor::process(const cpp2::CreateSnapshotReq&) {
   // step 2 : Blocking all writes action for storage engines.
   auto signRet = Snapshot::instance(kvstore_, client_)->blockingWrites(SignType::BLOCK_ON);
   if (signRet != nebula::cpp2::ErrorCode::SUCCEEDED) {
-    LOG(ERROR) << "Send blocking sign to storage engine error";
+    LOG(INFO) << "Send blocking sign to storage engine error";
     handleErrorCode(signRet);
     cancelWriteBlocking();
     onFinished();
@@ -77,7 +77,7 @@ void CreateSnapshotProcessor::process(const cpp2::CreateSnapshotReq&) {
   // step 3 : Create checkpoint for all storage engines and meta engine.
   auto csRet = Snapshot::instance(kvstore_, client_)->createSnapshot(snapshot);
   if (!nebula::ok(csRet)) {
-    LOG(ERROR) << "Checkpoint create error on storage engine";
+    LOG(INFO) << "Checkpoint create error on storage engine";
     handleErrorCode(nebula::error(csRet));
     cancelWriteBlocking();
     onFinished();
@@ -87,7 +87,7 @@ void CreateSnapshotProcessor::process(const cpp2::CreateSnapshotReq&) {
   // step 4 : checkpoint created done, so release the write blocking.
   auto unbRet = cancelWriteBlocking();
   if (unbRet != nebula::cpp2::ErrorCode::SUCCEEDED) {
-    LOG(ERROR) << "Create snapshot failed on meta server" << snapshot;
+    LOG(INFO) << "Create snapshot failed on meta server" << snapshot;
     handleErrorCode(unbRet);
     onFinished();
     return;
@@ -96,7 +96,7 @@ void CreateSnapshotProcessor::process(const cpp2::CreateSnapshotReq&) {
   // step 5 : create checkpoint for meta server.
   auto meteRet = kvstore_->createCheckpoint(kDefaultSpaceId, snapshot);
   if (meteRet.isLeftType()) {
-    LOG(ERROR) << "Create snapshot failed on meta server" << snapshot;
+    LOG(INFO) << "Create snapshot failed on meta server" << snapshot;
     handleErrorCode(nebula::cpp2::ErrorCode::E_STORE_FAILURE);
     onFinished();
     return;
@@ -109,10 +109,10 @@ void CreateSnapshotProcessor::process(const cpp2::CreateSnapshotReq&) {
 
   putRet = doSyncPut(std::move(data));
   if (putRet != nebula::cpp2::ErrorCode::SUCCEEDED) {
-    LOG(ERROR) << "All checkpoint creations are done, "
-                  "but update checkpoint status error. "
-                  "snapshot : "
-               << snapshot;
+    LOG(INFO) << "All checkpoint creations are done, "
+                 "but update checkpoint status error. "
+                 "snapshot : "
+              << snapshot;
     handleErrorCode(putRet);
   }
 
@@ -123,7 +123,7 @@ void CreateSnapshotProcessor::process(const cpp2::CreateSnapshotReq&) {
 nebula::cpp2::ErrorCode CreateSnapshotProcessor::cancelWriteBlocking() {
   auto signRet = Snapshot::instance(kvstore_, client_)->blockingWrites(SignType::BLOCK_OFF);
   if (signRet != nebula::cpp2::ErrorCode::SUCCEEDED) {
-    LOG(ERROR) << "Cancel write blocking error";
+    LOG(INFO) << "Cancel write blocking error";
     return signRet;
   }
   return nebula::cpp2::ErrorCode::SUCCEEDED;
diff --git a/src/meta/processors/admin/CreateSnapshotProcessor.h b/src/meta/processors/admin/CreateSnapshotProcessor.h
index 54f1dbd0c3d..d8936ce7b78 100644
--- a/src/meta/processors/admin/CreateSnapshotProcessor.h
+++ b/src/meta/processors/admin/CreateSnapshotProcessor.h
@@ -14,6 +14,10 @@
 namespace nebula {
 namespace meta {
 
+/**
+ * @brief Create snapshot for all spaces, will deprecated when backup ready
+ *
+ */
 class CreateSnapshotProcessor : public BaseProcessor<cpp2::ExecResp> {
  public:
   static CreateSnapshotProcessor* instance(kvstore::KVStore* kvstore, AdminClient* client) {
@@ -21,6 +25,11 @@ class CreateSnapshotProcessor : public BaseProcessor<cpp2::ExecResp> {
   }
   void process(const cpp2::CreateSnapshotReq& req);
 
+  /**
+   * @brief Cancel write blocking when create snapshot failed
+   *
+   * @return nebula::cpp2::ErrorCode
+   */
   nebula::cpp2::ErrorCode cancelWriteBlocking();
 
  private:
diff --git a/src/meta/processors/admin/DropSnapshotProcessor.cpp b/src/meta/processors/admin/DropSnapshotProcessor.cpp
index 140ae8c4bfe..e93e72a61f6 100644
--- a/src/meta/processors/admin/DropSnapshotProcessor.cpp
+++ b/src/meta/processors/admin/DropSnapshotProcessor.cpp
@@ -25,8 +25,8 @@ void DropSnapshotProcessor::process(const cpp2::DropSnapshotReq& req) {
       onFinished();
       return;
     }
-    LOG(ERROR) << "Get snapshot " << snapshot << " failed, error "
-               << apache::thrift::util::enumNameSafe(retCode);
+    LOG(INFO) << "Get snapshot " << snapshot << " failed, error "
+              << apache::thrift::util::enumNameSafe(retCode);
     handleErrorCode(retCode);
     onFinished();
     return;
@@ -36,7 +36,7 @@ void DropSnapshotProcessor::process(const cpp2::DropSnapshotReq& req) {
   auto hosts = MetaKeyUtils::parseSnapshotHosts(val);
   auto peersRet = NetworkUtils::toHosts(hosts);
   if (!peersRet.ok()) {
-    LOG(ERROR) << "Get checkpoint hosts error";
+    LOG(INFO) << "Get checkpoint hosts error";
     handleErrorCode(nebula::cpp2::ErrorCode::E_SNAPSHOT_FAILURE);
     onFinished();
     return;
@@ -46,16 +46,16 @@ void DropSnapshotProcessor::process(const cpp2::DropSnapshotReq& req) {
   auto peers = peersRet.value();
   auto dsRet = Snapshot::instance(kvstore_, client_)->dropSnapshot(snapshot, std::move(peers));
   if (dsRet != nebula::cpp2::ErrorCode::SUCCEEDED) {
-    LOG(ERROR) << "Drop snapshot error on storage engine";
+    LOG(INFO) << "Drop snapshot error on storage engine";
     // Need update the snapshot status to invalid, maybe some storage engine
     // drop done.
     data.emplace_back(MetaKeyUtils::snapshotKey(snapshot),
                       MetaKeyUtils::snapshotVal(cpp2::SnapshotStatus::INVALID, hosts));
     auto putRet = doSyncPut(std::move(data));
     if (putRet != nebula::cpp2::ErrorCode::SUCCEEDED) {
-      LOG(ERROR) << "Update snapshot status error. "
-                    "snapshot : "
-                 << snapshot;
+      LOG(INFO) << "Update snapshot status error. "
+                   "snapshot : "
+                << snapshot;
     }
     handleErrorCode(putRet);
     onFinished();
@@ -65,16 +65,16 @@ void DropSnapshotProcessor::process(const cpp2::DropSnapshotReq& req) {
   auto dmRet = kvstore_->dropCheckpoint(kDefaultSpaceId, snapshot);
   // TODO sky : need remove meta checkpoint from slave hosts.
   if (dmRet != nebula::cpp2::ErrorCode::SUCCEEDED) {
-    LOG(ERROR) << "Drop snapshot error on meta engine";
+    LOG(INFO) << "Drop snapshot error on meta engine";
     // Need update the snapshot status to invalid, maybe storage engines drop
     // done.
     data.emplace_back(MetaKeyUtils::snapshotKey(snapshot),
                       MetaKeyUtils::snapshotVal(cpp2::SnapshotStatus::INVALID, hosts));
     auto putRet = doSyncPut(std::move(data));
     if (putRet != nebula::cpp2::ErrorCode::SUCCEEDED) {
-      LOG(ERROR) << "Update snapshot status error. "
-                    "snapshot : "
-                 << snapshot;
+      LOG(INFO) << "Update snapshot status error. "
+                   "snapshot : "
+                << snapshot;
     }
     handleErrorCode(putRet);
     onFinished();
diff --git a/src/meta/processors/admin/DropSnapshotProcessor.h b/src/meta/processors/admin/DropSnapshotProcessor.h
index 50e56387ee8..6791635e4ed 100644
--- a/src/meta/processors/admin/DropSnapshotProcessor.h
+++ b/src/meta/processors/admin/DropSnapshotProcessor.h
@@ -14,6 +14,11 @@
 namespace nebula {
 namespace meta {
 
+/**
+ * @brief Drop snapshot for all spaces. It could drop snapshots
+ *        created by CreateBackupProcessor or CreateCheckpointProcessor.
+ *
+ */
 class DropSnapshotProcessor : public BaseProcessor<cpp2::ExecResp> {
  public:
   static DropSnapshotProcessor* instance(kvstore::KVStore* kvstore, AdminClient* client) {
diff --git a/src/meta/processors/admin/GetMetaDirInfoProcessor.cpp b/src/meta/processors/admin/GetMetaDirInfoProcessor.cpp
index 0d96ed730f6..122439b9138 100644
--- a/src/meta/processors/admin/GetMetaDirInfoProcessor.cpp
+++ b/src/meta/processors/admin/GetMetaDirInfoProcessor.cpp
@@ -19,8 +19,10 @@ void GetMetaDirInfoProcessor::process(const cpp2::GetMetaDirInfoReq& req) {
   nebula::cpp2::DirInfo dir;
   dir.data_ref() = datapaths;
   dir.root_ref() = boost::filesystem::current_path().string();
-  resp_.dir_ref() = std::move(dir);
+  VLOG(1) << "Get meta dir info, data paths size: " << dir.get_data().size()
+          << ", root path:" << dir.get_root();
 
+  resp_.dir_ref() = std::move(dir);
   resp_.code_ref() = nebula::cpp2::ErrorCode::SUCCEEDED;
   onFinished();
 }
diff --git a/src/meta/processors/admin/GetMetaDirInfoProcessor.h b/src/meta/processors/admin/GetMetaDirInfoProcessor.h
index 1dcf0f94cbc..bfe129f67dd 100644
--- a/src/meta/processors/admin/GetMetaDirInfoProcessor.h
+++ b/src/meta/processors/admin/GetMetaDirInfoProcessor.h
@@ -12,6 +12,11 @@
 namespace nebula {
 namespace meta {
 
+/**
+ * @brief Get meta dir info for each metad service, now only used in BR
+ *        Dir info contains root dir path and kv store data dir path.
+ *
+ */
 class GetMetaDirInfoProcessor : public BaseProcessor<cpp2::GetMetaDirInfoResp> {
  public:
   static GetMetaDirInfoProcessor* instance(kvstore::KVStore* kvstore) {
diff --git a/src/meta/processors/admin/HBProcessor.cpp b/src/meta/processors/admin/HBProcessor.cpp
index 83c2984f513..db61e2f8bce 100644
--- a/src/meta/processors/admin/HBProcessor.cpp
+++ b/src/meta/processors/admin/HBProcessor.cpp
@@ -35,7 +35,7 @@ void HBProcessor::process(const cpp2::HBReq& req) {
 
   if (role == cpp2::HostRole::STORAGE) {
     if (!ActiveHostsMan::machineRegisted(kvstore_, host)) {
-      LOG(ERROR) << "Machine " << host << " is not registed";
+      LOG(INFO) << "Machine " << host << " is not registed";
       handleErrorCode(nebula::cpp2::ErrorCode::E_MACHINE_NOT_FOUND);
       onFinished();
       return;
@@ -47,7 +47,7 @@ void HBProcessor::process(const cpp2::HBReq& req) {
       LOG(INFO) << "Set clusterId for new host " << host << "!";
       resp_.cluster_id_ref() = clusterId_;
     } else if (peerClusterId != clusterId_) {
-      LOG(ERROR) << "Reject wrong cluster host " << host << "!";
+      LOG(INFO) << "Reject wrong cluster host " << host << "!";
       handleErrorCode(nebula::cpp2::ErrorCode::E_WRONGCLUSTER);
       onFinished();
       return;
diff --git a/src/meta/processors/admin/HBProcessor.h b/src/meta/processors/admin/HBProcessor.h
index 4fde1b03bac..8b8caf5c358 100644
--- a/src/meta/processors/admin/HBProcessor.h
+++ b/src/meta/processors/admin/HBProcessor.h
@@ -31,6 +31,11 @@ struct HBCounters final {
 };
 extern HBCounters kHBCounters;
 
+/**
+ * @brief storaged/graphd/listener report info to metad periodically,
+ *        and update host alive info.
+ *
+ */
 class HBProcessor : public BaseProcessor<cpp2::HBResp> {
   FRIEND_TEST(HBProcessorTest, HBTest);
   FRIEND_TEST(MetaClientTest, HeartbeatTest);
diff --git a/src/meta/processors/admin/ListClusterInfoProcessor.cpp b/src/meta/processors/admin/ListClusterInfoProcessor.cpp
index 3c291fa9ca8..dbbbcfbe987 100644
--- a/src/meta/processors/admin/ListClusterInfoProcessor.cpp
+++ b/src/meta/processors/admin/ListClusterInfoProcessor.cpp
@@ -29,8 +29,8 @@ void ListClusterInfoProcessor::process(const cpp2::ListClusterInfoReq& req) {
   const auto& hostPrefix = MetaKeyUtils::hostPrefix();
   auto iterRet = doPrefix(hostPrefix);
   if (!nebula::ok(iterRet)) {
-    LOG(ERROR) << "get host prefix failed:"
-               << apache::thrift::util::enumNameSafe(nebula::error(iterRet));
+    LOG(INFO) << "get host prefix failed:"
+              << apache::thrift::util::enumNameSafe(nebula::error(iterRet));
     handleErrorCode(nebula::cpp2::ErrorCode::E_LIST_CLUSTER_FAILURE);
     onFinished();
     return;
@@ -49,10 +49,10 @@ void ListClusterInfoProcessor::process(const cpp2::ListClusterInfoReq& req) {
       auto dirKey = MetaKeyUtils::hostDirKey(addr.host, addr.port);
       auto dirRet = doGet(dirKey);
       if (!nebula::ok(dirRet)) {
-        LOG(ERROR) << folly::sformat("Get host {} dir info for {} failed: {}",
-                                     addr.toString(),
-                                     apache::thrift::util::enumNameSafe(info.role_),
-                                     apache::thrift::util::enumNameSafe(nebula::error(dirRet)));
+        LOG(INFO) << folly::sformat("Get host {} dir info for {} failed: {}",
+                                    addr.toString(),
+                                    apache::thrift::util::enumNameSafe(info.role_),
+                                    apache::thrift::util::enumNameSafe(nebula::error(dirRet)));
         handleErrorCode(nebula::error(dirRet));
         onFinished();
         return;
@@ -71,7 +71,7 @@ void ListClusterInfoProcessor::process(const cpp2::ListClusterInfoReq& req) {
   auto partRet = kvstore_->part(kDefaultSpaceId, kDefaultPartId);
   if (!nebula::ok(partRet)) {
     auto code = nebula::error(partRet);
-    LOG(ERROR) << "get meta part store failed, error: " << apache::thrift::util::enumNameSafe(code);
+    LOG(INFO) << "get meta part store failed, error: " << apache::thrift::util::enumNameSafe(code);
     handleErrorCode(nebula::cpp2::ErrorCode::E_LIST_CLUSTER_FAILURE);
     onFinished();
     return;
@@ -98,14 +98,14 @@ void ListClusterInfoProcessor::process(const cpp2::ListClusterInfoReq& req) {
       }
     }
     if (agentCount < 1) {
-      LOG(ERROR) << folly::sformat("There are {} agent count is host {}", agentCount, host);
+      LOG(INFO) << folly::sformat("There are {} agent count is host {}", agentCount, host);
       handleErrorCode(nebula::cpp2::ErrorCode::E_LIST_CLUSTER_NO_AGENT_FAILURE);
       onFinished();
       return;
     }
 
     if (services.size() <= 1) {
-      LOG(ERROR) << "There is no other service than agent in host: " << host;
+      LOG(INFO) << "There is no other service than agent in host: " << host;
       continue;
     }
   }
diff --git a/src/meta/processors/admin/ListClusterInfoProcessor.h b/src/meta/processors/admin/ListClusterInfoProcessor.h
index a62b098905d..9633e7df696 100644
--- a/src/meta/processors/admin/ListClusterInfoProcessor.h
+++ b/src/meta/processors/admin/ListClusterInfoProcessor.h
@@ -12,6 +12,11 @@
 namespace nebula {
 namespace meta {
 
+/**
+ * @brief Get cluster topology, grouping all the cluster service(metad/storaged/graphd/agent)
+ *        by hostname(or ip).
+ *        Now it is only used in BR tools.
+ */
 class ListClusterInfoProcessor : public BaseProcessor<cpp2::ListClusterInfoResp> {
  public:
   static ListClusterInfoProcessor* instance(kvstore::KVStore* kvstore) {
diff --git a/src/meta/processors/admin/ListSnapshotsProcessor.cpp b/src/meta/processors/admin/ListSnapshotsProcessor.cpp
index c1a14400737..aa4b808360a 100644
--- a/src/meta/processors/admin/ListSnapshotsProcessor.cpp
+++ b/src/meta/processors/admin/ListSnapshotsProcessor.cpp
@@ -15,7 +15,7 @@ void ListSnapshotsProcessor::process(const cpp2::ListSnapshotsReq&) {
   auto iterRet = doPrefix(prefix);
   if (!nebula::ok(iterRet)) {
     auto retCode = nebula::error(iterRet);
-    LOG(ERROR) << "Snapshot prefix failed, error: " << apache::thrift::util::enumNameSafe(retCode);
+    LOG(INFO) << "Snapshot prefix failed, error: " << apache::thrift::util::enumNameSafe(retCode);
     handleErrorCode(retCode);
     onFinished();
     return;
diff --git a/src/meta/processors/admin/ListSnapshotsProcessor.h b/src/meta/processors/admin/ListSnapshotsProcessor.h
index 59097ea905e..19dc70c9cde 100644
--- a/src/meta/processors/admin/ListSnapshotsProcessor.h
+++ b/src/meta/processors/admin/ListSnapshotsProcessor.h
@@ -11,6 +11,12 @@
 namespace nebula {
 namespace meta {
 
+/**
+ * @brief List all snapshot info, CreateBackupProcessor
+ *        and CreateCheckpointProcessor will both
+ *        add snapshot info to metad's kv store.
+ *
+ */
 class ListSnapshotsProcessor : public BaseProcessor<cpp2::ListSnapshotsResp> {
  public:
   static ListSnapshotsProcessor* instance(kvstore::KVStore* kvstore) {
diff --git a/src/meta/processors/admin/RestoreProcessor.cpp b/src/meta/processors/admin/RestoreProcessor.cpp
index 3f3c35e6cab..b785a784e0b 100644
--- a/src/meta/processors/admin/RestoreProcessor.cpp
+++ b/src/meta/processors/admin/RestoreProcessor.cpp
@@ -20,7 +20,7 @@ nebula::cpp2::ErrorCode RestoreProcessor::replaceHostInPartition(const HostAddr&
   auto iterRet = doPrefix(spacePrefix, direct);
   if (!nebula::ok(iterRet)) {
     retCode = nebula::error(iterRet);
-    LOG(ERROR) << "Space prefix failed, error: " << apache::thrift::util::enumNameSafe(retCode);
+    LOG(INFO) << "Space prefix failed, error: " << apache::thrift::util::enumNameSafe(retCode);
     return retCode;
   }
   auto iter = nebula::value(iterRet).get();
@@ -40,7 +40,7 @@ nebula::cpp2::ErrorCode RestoreProcessor::replaceHostInPartition(const HostAddr&
     auto iterPartRet = doPrefix(partPrefix, direct);
     if (!nebula::ok(iterPartRet)) {
       retCode = nebula::error(iterPartRet);
-      LOG(ERROR) << "Part prefix failed, error: " << apache::thrift::util::enumNameSafe(retCode);
+      LOG(INFO) << "Part prefix failed, error: " << apache::thrift::util::enumNameSafe(retCode);
       return retCode;
     }
     iter = nebula::value(iterPartRet).get();
@@ -64,8 +64,8 @@ nebula::cpp2::ErrorCode RestoreProcessor::replaceHostInPartition(const HostAddr&
   if (direct) {
     retCode = kvstore_->multiPutWithoutReplicator(kDefaultSpaceId, std::move(data));
     if (retCode != nebula::cpp2::ErrorCode::SUCCEEDED) {
-      LOG(ERROR) << "multiPutWithoutReplicator failed, error: "
-                 << apache::thrift::util::enumNameSafe(retCode);
+      LOG(INFO) << "multiPutWithoutReplicator partition info failed, error: "
+                << apache::thrift::util::enumNameSafe(retCode);
     }
     return retCode;
   }
@@ -90,7 +90,7 @@ nebula::cpp2::ErrorCode RestoreProcessor::replaceHostInZone(const HostAddr& ipv4
   auto iterRet = doPrefix(zonePrefix, direct);
   if (!nebula::ok(iterRet)) {
     retCode = nebula::error(iterRet);
-    LOG(ERROR) << "Zone prefix failed, error: " << apache::thrift::util::enumNameSafe(retCode);
+    LOG(INFO) << "Zone prefix failed, error: " << apache::thrift::util::enumNameSafe(retCode);
     return retCode;
   }
   auto iter = nebula::value(iterRet).get();
@@ -116,8 +116,8 @@ nebula::cpp2::ErrorCode RestoreProcessor::replaceHostInZone(const HostAddr& ipv4
   if (direct) {
     retCode = kvstore_->multiPutWithoutReplicator(kDefaultSpaceId, std::move(data));
     if (retCode != nebula::cpp2::ErrorCode::SUCCEEDED) {
-      LOG(ERROR) << "multiPutWithoutReplicator failed, error: "
-                 << apache::thrift::util::enumNameSafe(retCode);
+      LOG(INFO) << "multiPutWithoutReplicator zon info failed, error: "
+                << apache::thrift::util::enumNameSafe(retCode);
     }
     return retCode;
   }
@@ -136,7 +136,7 @@ nebula::cpp2::ErrorCode RestoreProcessor::replaceHostInZone(const HostAddr& ipv4
 void RestoreProcessor::process(const cpp2::RestoreMetaReq& req) {
   auto files = req.get_files();
   if (files.empty()) {
-    LOG(ERROR) << "restore must contain the sst file.";
+    LOG(INFO) << "restore must contain the sst file.";
     handleErrorCode(nebula::cpp2::ErrorCode::E_RESTORE_FAILURE);
     onFinished();
     return;
@@ -144,7 +144,7 @@ void RestoreProcessor::process(const cpp2::RestoreMetaReq& req) {
 
   auto ret = kvstore_->restoreFromFiles(kDefaultSpaceId, files);
   if (ret != nebula::cpp2::ErrorCode::SUCCEEDED) {
-    LOG(ERROR) << "Failed to restore file";
+    LOG(INFO) << "Failed to restore file";
     handleErrorCode(nebula::cpp2::ErrorCode::E_RESTORE_FAILURE);
     onFinished();
     return;
@@ -159,7 +159,7 @@ void RestoreProcessor::process(const cpp2::RestoreMetaReq& req) {
 
       auto result = replaceHostInPartition(h.get_from_host(), h.get_to_host(), true);
       if (result != nebula::cpp2::ErrorCode::SUCCEEDED) {
-        LOG(ERROR) << "replaceHost in partition fails when recovered";
+        LOG(INFO) << "replaceHost in partition fails when recovered";
         handleErrorCode(result);
         onFinished();
         return;
@@ -167,11 +167,13 @@ void RestoreProcessor::process(const cpp2::RestoreMetaReq& req) {
 
       result = replaceHostInZone(h.get_from_host(), h.get_to_host(), true);
       if (result != nebula::cpp2::ErrorCode::SUCCEEDED) {
-        LOG(ERROR) << "replaceHost in zone fails when recovered";
+        LOG(INFO) << "replaceHost in zone fails when recovered";
         handleErrorCode(result);
         onFinished();
         return;
       }
+
+      // TODO(spw): need to replace the registered machine
     }
   }
 
diff --git a/src/meta/processors/admin/RestoreProcessor.h b/src/meta/processors/admin/RestoreProcessor.h
index c9b10ffbd80..b980ffd7f79 100644
--- a/src/meta/processors/admin/RestoreProcessor.h
+++ b/src/meta/processors/admin/RestoreProcessor.h
@@ -13,6 +13,11 @@
 namespace nebula {
 namespace meta {
 
+/**
+ * @brief Rebuild the host relative info after ingesting the table backup data to
+ *        the new cluster metad KV store.
+ *
+ */
 class RestoreProcessor : public BaseProcessor<cpp2::ExecResp> {
  public:
   static RestoreProcessor* instance(kvstore::KVStore* kvstore) {
diff --git a/src/meta/processors/admin/SnapShot.cpp b/src/meta/processors/admin/SnapShot.cpp
index 49452bd83d5..0f71c257ad3 100644
--- a/src/meta/processors/admin/SnapShot.cpp
+++ b/src/meta/processors/admin/SnapShot.cpp
@@ -85,9 +85,8 @@ nebula::cpp2::ErrorCode Snapshot::dropSnapshot(const std::string& name,
     auto status = client_->dropSnapshot(spaces, name, host).get();
     if (!status.ok()) {
       auto msg = "failed drop checkpoint : \"%s\". on host %s. error %s";
-      auto error = folly::stringPrintf(
+      LOG(INFO) << folly::stringPrintf(
           msg, name.c_str(), host.toString().c_str(), status.toString().c_str());
-      LOG(ERROR) << error;
     }
   }
   return nebula::cpp2::ErrorCode::SUCCEEDED;
@@ -109,8 +108,8 @@ nebula::cpp2::ErrorCode Snapshot::blockingWrites(storage::cpp2::EngineSignType s
     LOG(INFO) << "will block write host: " << host;
     auto status = client_->blockingWrites(spaces, sign, host).get();
     if (!status.ok()) {
-      LOG(ERROR) << "Send blocking sign error on host " << host
-                 << ", errorcode: " << status.message();
+      LOG(INFO) << "Send blocking sign error on host " << host
+                << ", errorcode: " << status.message();
       ret = nebula::cpp2::ErrorCode::E_BLOCK_WRITE_FAILURE;
       if (sign == storage::cpp2::EngineSignType::BLOCK_ON) {
         break;
@@ -127,8 +126,8 @@ Snapshot::getHostSpaces() {
   std::unique_ptr<kvstore::KVIterator> iter;
   auto retCode = kv_->prefix(kDefaultSpaceId, kDefaultPartId, prefix, &iter);
   if (retCode != nebula::cpp2::ErrorCode::SUCCEEDED) {
-    LOG(ERROR) << "Get hosts meta data failed, error: "
-               << apache::thrift::util::enumNameSafe(retCode);
+    LOG(INFO) << "Get hosts meta data failed, error: "
+              << apache::thrift::util::enumNameSafe(retCode);
     return retCode;
   }
 
diff --git a/src/meta/processors/admin/SnapShot.h b/src/meta/processors/admin/SnapShot.h
index 0c1d9e7b124..b6c129f9742 100644
--- a/src/meta/processors/admin/SnapShot.h
+++ b/src/meta/processors/admin/SnapShot.h
@@ -17,6 +17,12 @@
 namespace nebula {
 namespace meta {
 
+/**
+ * @brief Create and drop snapshots for given spaces in
+ *        storage hosts(include followers)
+ *        Another feature is providing blocking/unbloking writings.
+ *
+ */
 class Snapshot {
  public:
   static Snapshot* instance(kvstore::KVStore* kv, AdminClient* client) {
@@ -34,8 +40,22 @@ class Snapshot {
           std::unordered_map<GraphSpaceID, std::vector<cpp2::HostBackupInfo>>>
   createSnapshot(const std::string& name);
 
+  /**
+   * @brief Drop specified snapshot in given storage hosts
+   *
+   * @param name snapshot name
+   * @param hosts storage hosts
+   * @return nebula::cpp2::ErrorCode
+   */
   nebula::cpp2::ErrorCode dropSnapshot(const std::string& name, const std::vector<HostAddr>& hosts);
 
+  /**
+   * @brief Blocking writings before create snapshot, allow writings after create
+   *        snapshot failed or completely
+   *
+   * @param sign BLOCK_ON and BLOCK_OFF(allow)
+   * @return nebula::cpp2::ErrorCode
+   */
   nebula::cpp2::ErrorCode blockingWrites(storage::cpp2::EngineSignType sign);
 
  private: