diff --git a/CMakeLists.txt b/CMakeLists.txt
index 4d68f38dd..f356b9288 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -51,6 +51,7 @@ add_executable(vl_test
         ${PROJECT_SOURCE_DIR}/visualdl/logic/sdk_test.cc
         ${PROJECT_SOURCE_DIR}/visualdl/logic/histogram_test.cc
         ${PROJECT_SOURCE_DIR}/visualdl/storage/storage_test.cc
+        ${PROJECT_SOURCE_DIR}/visualdl/storage/test_binary_record.cc
         ${PROJECT_SOURCE_DIR}/visualdl/utils/test_concurrency.cc
         ${PROJECT_SOURCE_DIR}/visualdl/utils/test_image.cc
         ${PROJECT_SOURCE_DIR}/visualdl/utils/concurrency.h
diff --git a/visualdl/logic/sdk.cc b/visualdl/logic/sdk.cc
index d252ae3d0..338c29fba 100644
--- a/visualdl/logic/sdk.cc
+++ b/visualdl/logic/sdk.cc
@@ -1,11 +1,83 @@
 #include "visualdl/logic/sdk.h"
 
 #include "visualdl/logic/histogram.h"
+#include "visualdl/storage/binary_record.h"
 #include "visualdl/utils/image.h"
 #include "visualdl/utils/macro.h"
 
 namespace visualdl {
 
+// global log dir, a hack solution to pass accross all the components.
+// One process of VDL backend can only process a single logdir, so this
+// is OK.
+std::string g_log_dir;
+
+LogWriter LogWriter::AsMode(const std::string& mode) {
+  LogWriter writer = *this;
+  storage_.AddMode(mode);
+  writer.mode_ = mode;
+  return writer;
+}
+
+Tablet LogWriter::AddTablet(const std::string& tag) {
+  // TODO(ChunweiYan) add string check here.
+  auto tmp = mode_ + "/" + tag;
+  string::TagEncode(tmp);
+  auto res = storage_.AddTablet(tmp);
+  res.SetCaptions(std::vector<std::string>({mode_}));
+  res.SetTag(mode_, tag);
+  return res;
+}
+
+LogReader::LogReader(const std::string& dir) : reader_(dir) { g_log_dir = dir; }
+
+LogReader LogReader::AsMode(const std::string& mode) {
+  auto tmp = *this;
+  tmp.mode_ = mode;
+  return tmp;
+}
+
+TabletReader LogReader::tablet(const std::string& tag) {
+  auto tmp = mode_ + "/" + tag;
+  string::TagEncode(tmp);
+  return reader_.tablet(tmp);
+}
+
+std::vector<std::string> LogReader::all_tags() {
+  auto tags = reader_.all_tags();
+  auto it =
+      std::remove_if(tags.begin(), tags.end(), [&](const std::string& tag) {
+        return !TagMatchMode(tag, mode_);
+      });
+  tags.erase(it + 1);
+  return tags;
+}
+
+std::vector<std::string> LogReader::tags(const std::string& component) {
+  auto type = Tablet::type(component);
+  auto tags = reader_.tags(type);
+  CHECK(!tags.empty()) << "component " << component << " has no taged records";
+  std::vector<std::string> res;
+  for (const auto& tag : tags) {
+    if (TagMatchMode(tag, mode_)) {
+      res.push_back(GenReadableTag(mode_, tag));
+    }
+  }
+  return res;
+}
+
+std::string LogReader::GenReadableTag(const std::string& mode,
+                                      const std::string& tag) {
+  auto tmp = tag;
+  string::TagDecode(tmp);
+  return tmp.substr(mode.size() + 1);  // including `/`
+}
+
+bool LogReader::TagMatchMode(const std::string& tag, const std::string& mode) {
+  if (tag.size() <= mode.size()) return false;
+  return tag.substr(0, mode.size()) == mode;
+}
+
 namespace components {
 
 template <typename T>
@@ -103,8 +175,10 @@ void Image::SetSample(int index,
     new_shape.emplace_back(1);
   }
   // production
-  int size = std::accumulate(
-          new_shape.begin(), new_shape.end(), 1., [](int a, int b) { return a * b; });
+  int size =
+      std::accumulate(new_shape.begin(), new_shape.end(), 1., [](int a, int b) {
+        return a * b;
+      });
   CHECK_GT(size, 0);
   CHECK_LE(new_shape.size(), 3)
       << "shape should be something like (width, height, num_channel)";
@@ -114,7 +188,6 @@ void Image::SetSample(int index,
   CHECK_LT(index, num_samples_);
   CHECK_LE(index, num_records_);
 
-  auto entry = step_.MutableData<std::vector<byte_t>>(index);
   // trick to store int8 to protobuf
   std::vector<byte_t> data_str(data.size());
   for (int i = 0; i < data.size(); i++) {
@@ -122,9 +195,14 @@ void Image::SetSample(int index,
   }
   Uint8Image image(new_shape[2], new_shape[0] * new_shape[1]);
   NormalizeImage(&image, &data[0], new_shape[0] * new_shape[1], new_shape[2]);
-  // entry.SetRaw(std::string(data_str.begin(), data_str.end()));
-  entry.SetRaw(
+
+  BinaryRecord brcd(
+      GenBinaryRecordDir(step_.parent()->dir()),
       std::string(image.data(), image.data() + image.rows() * image.cols()));
+  brcd.tofile();
+
+  auto entry = step_.MutableData<std::vector<byte_t>>(index);
+  entry.SetRaw(brcd.hash());
 
   static_assert(
       !is_same_type<value_t, shape_t>::value,
@@ -132,12 +210,6 @@ void Image::SetSample(int index,
 
   // set meta.
   entry.SetMulti(new_shape);
-
-  // // set meta with hack
-  // Entry<shape_t> meta;
-  // meta.set_parent(entry.parent());
-  // meta.entry = entry.entry;
-  // meta.SetMulti(shape);
 }
 
 std::string ImageReader::caption() {
@@ -154,9 +226,13 @@ ImageReader::ImageRecord ImageReader::record(int offset, int index) {
   ImageRecord res;
   auto record = reader_.record(offset);
   auto entry = record.data(index);
-  auto data_str = entry.GetRaw();
-  std::transform(data_str.begin(),
-                 data_str.end(),
+  auto data_hash = entry.GetRaw();
+  CHECK(!g_log_dir.empty())
+      << "g_log_dir should be set in LogReader construction";
+  BinaryRecordReader brcd(GenBinaryRecordDir(g_log_dir), data_hash);
+
+  std::transform(brcd.data.begin(),
+                 brcd.data.end(),
                  std::back_inserter(res.data),
                  [](byte_t i) { return (int)(i); });
   res.shape = entry.GetMulti<shape_t>();
diff --git a/visualdl/logic/sdk.h b/visualdl/logic/sdk.h
index 88b959904..37c5e1849 100644
--- a/visualdl/logic/sdk.h
+++ b/visualdl/logic/sdk.h
@@ -31,25 +31,9 @@ class LogWriter {
     storage_.AddMode(mode);
   }
 
-  LogWriter AsMode(const std::string& mode) {
-    LogWriter writer = *this;
-    storage_.AddMode(mode);
-    writer.mode_ = mode;
-    return writer;
-  }
+  LogWriter AsMode(const std::string& mode);
 
-  /**
-   * create a new tablet
-   */
-  Tablet AddTablet(const std::string& tag) {
-    // TODO(ChunweiYan) add string check here.
-    auto tmp = mode_ + "/" + tag;
-    string::TagEncode(tmp);
-    auto res = storage_.AddTablet(tmp);
-    res.SetCaptions(std::vector<std::string>({mode_}));
-    res.SetTag(mode_, tag);
-    return res;
-  }
+  Tablet AddTablet(const std::string& tag);
 
   Storage& storage() { return storage_; }
 
@@ -64,61 +48,26 @@ class LogWriter {
  */
 class LogReader {
 public:
-  LogReader(const std::string& dir) : reader_(dir) {}
+  LogReader(const std::string& dir);
 
   void SetMode(const std::string& mode) { mode_ = mode; }
 
-  LogReader AsMode(const std::string& mode) {
-    auto tmp = *this;
-    tmp.mode_ = mode;
-    return tmp;
-  }
+  LogReader AsMode(const std::string& mode);
 
   const std::string& mode() { return mode_; }
 
-  TabletReader tablet(const std::string& tag) {
-    auto tmp = mode_ + "/" + tag;
-    string::TagEncode(tmp);
-    return reader_.tablet(tmp);
-  }
+  TabletReader tablet(const std::string& tag);
 
-  std::vector<std::string> all_tags() {
-    auto tags = reader_.all_tags();
-    auto it =
-        std::remove_if(tags.begin(), tags.end(), [&](const std::string& tag) {
-          return !TagMatchMode(tag, mode_);
-        });
-    tags.erase(it + 1);
-    return tags;
-  }
+  std::vector<std::string> all_tags();
 
-  std::vector<std::string> tags(const std::string& component) {
-    auto type = Tablet::type(component);
-    auto tags = reader_.tags(type);
-    CHECK(!tags.empty()) << "component " << component
-                         << " has no taged records";
-    std::vector<std::string> res;
-    for (const auto& tag : tags) {
-      if (TagMatchMode(tag, mode_)) {
-        res.push_back(GenReadableTag(mode_, tag));
-      }
-    }
-    return res;
-  }
+  std::vector<std::string> tags(const std::string& component);
 
   StorageReader& storage() { return reader_; }
 
   static std::string GenReadableTag(const std::string& mode,
-                                    const std::string& tag) {
-    auto tmp = tag;
-    string::TagDecode(tmp);
-    return tmp.substr(mode.size() + 1);  // including `/`
-  }
+                                    const std::string& tag);
 
-  static bool TagMatchMode(const std::string& tag, const std::string& mode) {
-    if (tag.size() <= mode.size()) return false;
-    return tag.substr(0, mode.size()) == mode;
-  }
+  static bool TagMatchMode(const std::string& tag, const std::string& mode);
 
 protected:
 private:
diff --git a/visualdl/server/lib.py b/visualdl/server/lib.py
index 23fa7b959..3d890badb 100644
--- a/visualdl/server/lib.py
+++ b/visualdl/server/lib.py
@@ -137,11 +137,6 @@ def get_invididual_image(storage, mode, tag, step_index, max_size=80):
         data = np.array(record.data(), dtype='uint8').reshape(shape)
         tempfile = NamedTemporaryFile(mode='w+b', suffix='.png')
         with Image.fromarray(data) as im:
-            size = max(shape[0], shape[1])
-            if size > max_size:
-                scale = max_size * 1. / size
-                scaled_shape = (int(shape[0] * scale), int(shape[1] * scale))
-                im = im.resize(scaled_shape)
             im.save(tempfile)
         tempfile.seek(0, 0)
         return tempfile
diff --git a/visualdl/storage/binary_record.h b/visualdl/storage/binary_record.h
new file mode 100644
index 000000000..8eeab7810
--- /dev/null
+++ b/visualdl/storage/binary_record.h
@@ -0,0 +1,80 @@
+#ifndef VISUALDL_STORAGE_BINARY_RECORD_H
+#define VISUALDL_STORAGE_BINARY_RECORD_H
+
+#include <fstream>
+#include <functional>
+
+#include "visualdl/utils/filesystem.h"
+
+namespace visualdl {
+
+static std::string GenBinaryRecordDir(const std::string& dir) {
+  return dir + "/binary_records";
+}
+
+// A storage helper to save large file(currently just for Image component).
+// The protobuf message has some limitation on meassage size, and LogWriter
+// will maintain a memory of all the messages, it is bad to store images
+// directly in protobuf. So a simple binary storage is used to serialize images
+// to disk.
+struct BinaryRecord {
+  std::hash<std::string> hasher;
+
+  BinaryRecord(const std::string dir, std::string&& data)
+      : data_(data), dir_(dir) {
+    hash_ = std::to_string(hasher(data));
+    path_ = dir + "/" + hash();
+  }
+
+  const std::string& path() { return path_; }
+
+  void tofile() {
+    fs::TryRecurMkdir(dir_);
+    std::fstream file(path_, file.binary | file.out);
+    CHECK(file.is_open()) << "open " << path_ << " failed";
+
+    size_t size = data_.size();
+    file.write(reinterpret_cast<char*>(&size), sizeof(size));
+    file.write(data_.data(), data_.size());
+  }
+
+  const std::string& hash() { return hash_; }
+
+private:
+  std::string dir_;
+  std::string path_;
+  std::string data_;
+  std::string hash_;
+};
+
+struct BinaryRecordReader {
+  std::string data;
+  std::hash<std::string> hasher;
+
+  BinaryRecordReader(const std::string& dir, const std::string& hash)
+      : dir_(dir), hash_(hash) {
+    fromfile();
+  }
+  std::string hash() { return std::to_string(hasher(data)); }
+
+protected:
+  void fromfile() {
+    std::string path = dir_ + "/" + hash_;
+    std::ifstream file(path, file.binary);
+    CHECK(file.is_open()) << " failed to open file " << path;
+
+    size_t size;
+    file.read(reinterpret_cast<char*>(&size), sizeof(size_t));
+    data.resize(size);
+    file.read(&data[0], size);
+
+    CHECK_EQ(hash(), hash_) << "data broken: " << path;
+  }
+
+private:
+  std::string dir_;
+  std::string hash_;
+};
+
+}  // namespace visualdl
+#endif
diff --git a/visualdl/storage/test_binary_record.cc b/visualdl/storage/test_binary_record.cc
new file mode 100644
index 000000000..c995f1df7
--- /dev/null
+++ b/visualdl/storage/test_binary_record.cc
@@ -0,0 +1,15 @@
+#include "visualdl/storage/binary_record.h"
+
+#include <gtest/gtest.h>
+
+using namespace visualdl;
+
+TEST(BinaryRecord, init) {
+  std::string message = "hello world";
+  BinaryRecord rcd("./", std::move(message));
+  rcd.tofile();
+
+  BinaryRecordReader reader("./", rcd.hash());
+  LOG(INFO) << reader.data;
+  ASSERT_EQ(reader.data, "hello world");
+}
diff --git a/visualdl/utils/filesystem.h b/visualdl/utils/filesystem.h
index 5569922bd..b993e86d5 100644
--- a/visualdl/utils/filesystem.h
+++ b/visualdl/utils/filesystem.h
@@ -7,6 +7,8 @@
 #include <unistd.h>
 #include <fstream>
 
+#include "visualdl/utils/logging.h"
+
 namespace visualdl {
 
 namespace fs {
@@ -44,7 +46,6 @@ bool DeSerializeFromFile(T* proto, const std::string& path) {
 }
 
 static void TryMkdir(const std::string& dir) {
-//  VLOG(1) << "try to mkdir " << dir;
   struct stat st = {0};
   if (stat(dir.c_str(), &st) == -1) {
     ::mkdir(dir.c_str(), 0700);
@@ -67,7 +68,6 @@ static void TryRecurMkdir(const std::string& path) {
 inline void Write(const std::string& path,
                   const std::string& buffer,
                   std::ios::openmode open_mode = std::ios::binary) {
-  VLOG(1) << "write to path " << path;
   std::ofstream file(path, open_mode);
   CHECK(file.is_open()) << "failed to open " << path;
   file.write(buffer.c_str(), buffer.size());
@@ -76,7 +76,6 @@ inline void Write(const std::string& path,
 
 inline std::string Read(const std::string& path,
                         std::ios::openmode open_mode = std::ios::binary) {
-  VLOG(1) << "read from path " << path;
   std::string buffer;
   std::ifstream file(path, open_mode | std::ios::ate);
   CHECK(file.is_open()) << "failed to open " << path;