diff --git a/config/options.go b/config/options.go
index beafe9ea..54651768 100644
--- a/config/options.go
+++ b/config/options.go
@@ -7,6 +7,7 @@ type Options struct {
 	DataFileSize int64  //数据文件的大小
 	SyncWrite    bool   // 每次写数据是否持久化
 	IndexType    IndexerType
+	FIOType      FIOType
 }
 
 // IteratorOptions 索引迭代器配置项
@@ -25,6 +26,14 @@ type WriteBatchOptions struct {
 	SyncWrites bool
 }
 
+type FIOType = int8
+
+const (
+	FileIOType = iota + 1 // Standard File IO
+	BufIOType             // File IO with buffer
+	MmapIOType            // Memory Mapping IO
+)
+
 type IndexerType = int8
 
 const (
@@ -40,6 +49,7 @@ var DefaultOptions = Options{
 	DataFileSize: 256 * 1024 * 1024, // 256MB
 	SyncWrite:    false,
 	IndexType:    Btree,
+	FIOType:      FileIOType,
 }
 
 var DefaultIteratorOptions = IteratorOptions{
diff --git a/data/data_file.go b/data/data_file.go
index 204be527..375b95cc 100644
--- a/data/data_file.go
+++ b/data/data_file.go
@@ -22,9 +22,9 @@ type DataFile struct {
 }
 
 // OpenDataFile 打开新的数据文件
-func OpenDataFile(dirPath string, fildID uint32) (*DataFile, error) {
+func OpenDataFile(dirPath string, fildID uint32, fileSize int64, fioType int8) (*DataFile, error) {
 	fileName := GetDataFileName(dirPath, fildID)
-	return newDataFile(fileName, fildID)
+	return newDataFile(fileName, fildID, fileSize, fioType)
 }
 
 func GetDataFileName(dirPath string, fildID uint32) string {
@@ -32,20 +32,20 @@ func GetDataFileName(dirPath string, fildID uint32) string {
 }
 
 // OpenHintFile 打开 Hint 索引文件
-func OpenHintFile(dirPath string) (*DataFile, error) {
+func OpenHintFile(dirPath string, fileSize int64, fioType int8) (*DataFile, error) {
 	fileName := filepath.Join(dirPath, HintFileSuffix)
-	return newDataFile(fileName, 0)
+	return newDataFile(fileName, 0, fileSize, fioType)
 }
 
 // OpenMergeFinaFile 打开标识 merge 完成的文件
-func OpenMergeFinaFile(dirPath string) (*DataFile, error) {
+func OpenMergeFinaFile(dirPath string, fileSize int64, fioType int8) (*DataFile, error) {
 	fileName := filepath.Join(dirPath, MergeFinaFileSuffix)
-	return newDataFile(fileName, 0)
+	return newDataFile(fileName, 0, fileSize, fioType)
 }
 
-func newDataFile(dirPath string, fildID uint32) (*DataFile, error) {
+func newDataFile(dirPath string, fildID uint32, fileSize int64, fioType int8) (*DataFile, error) {
 	//初始化 IOManager 管理器接口
-	ioManager, err := fio.NewIOManager(dirPath)
+	ioManager, err := fio.NewIOManager(dirPath, fileSize, fioType)
 	if err != nil {
 		return nil, err
 	}
diff --git a/data/data_file_test.go b/data/data_file_test.go
index 98b5a821..545ae58c 100644
--- a/data/data_file_test.go
+++ b/data/data_file_test.go
@@ -1,27 +1,30 @@
 package data
 
 import (
+	"github.com/ByteStorage/FlyDB/fio"
 	"github.com/stretchr/testify/assert"
 	"os"
 	"testing"
 )
 
+const DefaultFileSize = 256 * 1024 * 1024
+
 func TestOpenDataFile(t *testing.T) {
-	dataFile1, err := OpenDataFile(os.TempDir(), 0)
+	dataFile1, err := OpenDataFile(os.TempDir(), 0, DefaultFileSize, fio.FileIOType)
 	assert.Nil(t, err)
 	assert.NotNil(t, dataFile1)
 
-	dataFile2, err := OpenDataFile(os.TempDir(), 1)
+	dataFile2, err := OpenDataFile(os.TempDir(), 1, DefaultFileSize, fio.FileIOType)
 	assert.Nil(t, err)
 	assert.NotNil(t, dataFile2)
 
-	dataFile3, err := OpenDataFile(os.TempDir(), 1)
+	dataFile3, err := OpenDataFile(os.TempDir(), 1, DefaultFileSize, fio.FileIOType)
 	assert.Nil(t, err)
 	assert.NotNil(t, dataFile3)
 }
 
 func TestDataFile_Write(t *testing.T) {
-	dataFile, err := OpenDataFile(os.TempDir(), 12312)
+	dataFile, err := OpenDataFile(os.TempDir(), 12312, DefaultFileSize, fio.FileIOType)
 	assert.Nil(t, err)
 	assert.NotNil(t, dataFile)
 
@@ -36,7 +39,7 @@ func TestDataFile_Write(t *testing.T) {
 }
 
 func TestDataFile_Close(t *testing.T) {
-	dataFile, err := OpenDataFile(os.TempDir(), 1111111)
+	dataFile, err := OpenDataFile(os.TempDir(), 1111111, DefaultFileSize, fio.FileIOType)
 	assert.Nil(t, err)
 	assert.NotNil(t, dataFile)
 
@@ -45,7 +48,7 @@ func TestDataFile_Close(t *testing.T) {
 }
 
 func TestDataFile_Sync(t *testing.T) {
-	dataFile, err := OpenDataFile(os.TempDir(), 2222222)
+	dataFile, err := OpenDataFile(os.TempDir(), 2222222, DefaultFileSize, fio.FileIOType)
 	assert.Nil(t, err)
 	assert.NotNil(t, dataFile)
 
@@ -54,7 +57,7 @@ func TestDataFile_Sync(t *testing.T) {
 }
 
 func TestDataFile_ReadLogRecord(t *testing.T) {
-	dataFile, err := OpenDataFile(os.TempDir(), 123)
+	dataFile, err := OpenDataFile(os.TempDir(), 123, DefaultFileSize, fio.FileIOType)
 	assert.Nil(t, err)
 	assert.NotNil(t, dataFile)
 
diff --git a/engine/db.go b/engine/db.go
index 92ddc4fa..cbbf6109 100644
--- a/engine/db.go
+++ b/engine/db.go
@@ -218,7 +218,7 @@ func (db *DB) setActiveDataFile() error {
 	}
 
 	// Open a new data file
-	dataFile, err := data.OpenDataFile(db.options.DirPath, initialFileID)
+	dataFile, err := data.OpenDataFile(db.options.DirPath, initialFileID, db.options.DataFileSize, db.options.FIOType)
 	if err != nil {
 		return err
 	}
@@ -368,7 +368,7 @@ func (db *DB) loadDataFiles() error {
 
 	// Walk through each file id and open the corresponding data file
 	for i, fid := range fileIds {
-		dataFile, err := data.OpenDataFile(db.options.DirPath, uint32(fid))
+		dataFile, err := data.OpenDataFile(db.options.DirPath, uint32(fid), db.options.DataFileSize, db.options.FIOType)
 		if err != nil {
 			return err
 		}
diff --git a/engine/merge.go b/engine/merge.go
index e8637875..4fff22e6 100755
--- a/engine/merge.go
+++ b/engine/merge.go
@@ -85,7 +85,7 @@ func (db *DB) Merge() error {
 	}
 
 	// 打开 hint 文件存储索引
-	hintFile, err := data.OpenHintFile(mergePath)
+	hintFile, err := data.OpenHintFile(mergePath, db.options.DataFileSize, db.options.FIOType)
 	if err != nil {
 		return err
 	}
@@ -131,7 +131,7 @@ func (db *DB) Merge() error {
 	}
 
 	// 写标识 merge 完成的文件
-	mergeFinaFile, err := data.OpenMergeFinaFile(mergePath)
+	mergeFinaFile, err := data.OpenMergeFinaFile(mergePath, db.options.DataFileSize, db.options.FIOType)
 	if err != nil {
 		return err
 	}
@@ -223,7 +223,7 @@ func (db *DB) loadMergeFiles() error {
 
 // 获取最近没有参与 merge 的文件 id
 func (db *DB) getRecentlyNonMergeFileId(dirPath string) (uint32, error) {
-	mergeFinaFile, err := data.OpenMergeFinaFile(dirPath)
+	mergeFinaFile, err := data.OpenMergeFinaFile(dirPath, db.options.DataFileSize, db.options.FIOType)
 	if err != nil {
 		return 0, err
 	}
@@ -247,7 +247,7 @@ func (db *DB) loadIndexFromHintFile() error {
 	}
 
 	// 打开 hint 文件
-	hintFile, err := data.OpenHintFile(db.options.DirPath)
+	hintFile, err := data.OpenHintFile(db.options.DirPath, db.options.DataFileSize, db.options.FIOType)
 	if err != nil {
 		return err
 	}
diff --git a/fio/file_io.go b/fio/file_io.go
index 28efcc50..50e7dcbc 100644
--- a/fio/file_io.go
+++ b/fio/file_io.go
@@ -45,7 +45,3 @@ func (fio *FileIO) Size() (int64, error) {
 	}
 	return stat.Size(), nil
 }
-
-func NewIOManager(filename string) (IOManager, error) {
-	return NewFileIOManager(filename)
-}
diff --git a/fio/io_manager.go b/fio/io_manager.go
index 3f62b89c..f2898024 100644
--- a/fio/io_manager.go
+++ b/fio/io_manager.go
@@ -2,6 +2,14 @@ package fio
 
 const DataFilePerm = 0644 //0644 表示创建了一个文件，文件所有者可以读写，其他人只能读
 
+const DefaultFileSize = 256 * 1024 * 1024
+
+const (
+	FileIOType = iota + 1 // Standard File IO
+	BufIOType             // File IO with buffer
+	MmapIOType            // Memory Mapping IO
+)
+
 // IOManager 抽象 IO 管理接口， 可以接入不同的 IO 类型， 目前支持标准文件 IO
 type IOManager interface {
 	// Read 从文件的给定位置读取对应的数据
@@ -19,3 +27,16 @@ type IOManager interface {
 	// Size get file size
 	Size() (int64, error)
 }
+
+// NewIOManager get IOManager based on type
+func NewIOManager(filename string, fileSize int64, fioType int8) (IOManager, error) {
+	switch fioType {
+	case FileIOType:
+		return NewFileIOManager(filename)
+	case BufIOType:
+		return NewBufIOManager(filename)
+	case MmapIOType:
+		return NewMMapIOManager(filename, fileSize)
+	}
+	return NewFileIOManager(filename)
+}
diff --git a/fio/mmap_io.go b/fio/mmap_io.go
index 8bd885a7..5bc20cd0 100644
--- a/fio/mmap_io.go
+++ b/fio/mmap_io.go
@@ -7,20 +7,18 @@ import (
 	"unsafe"
 )
 
-// DefaultMemMapSize 最大映射内存大小
-const DefaultMemMapSize = 256 * 1024 * 1024
-
-// MMapIO 标准系统文件IO
 type MMapIO struct {
-	fd     *os.File // 系统文件描述符
-	data   []byte   // 与文件对应的映射区
-	dirty  bool     // 是否更改过
-	offset int64    // 写入位置
+	fd       *os.File // system file descriptor
+	data     []byte   // the mapping area corresponding to the file
+	dirty    bool     // has changed
+	offset   int64    // next write location
+	fileSize int64    // max file size
 }
 
-// NewMMapIOManager 初始化标准文件 IO
-func NewMMapIOManager(fileName string) (*MMapIO, error) {
-	mmapIO := &MMapIO{}
+// NewMMapIOManager Initialize Mmap IO
+func NewMMapIOManager(fileName string, fileSize int64) (*MMapIO, error) {
+	mmapIO := &MMapIO{fileSize: fileSize}
+
 	fd, err := os.OpenFile(
 		fileName,
 		os.O_CREATE|os.O_RDWR|os.O_APPEND,
@@ -31,13 +29,13 @@ func NewMMapIOManager(fileName string) (*MMapIO, error) {
 	}
 	info, _ := fd.Stat()
 
-	// 将文件扩容到映射区大小, 保存时会裁剪
-	if err := fd.Truncate(DefaultMemMapSize); err != nil {
+	// Expand files to maximum file size, crop when saving
+	if err := fd.Truncate(fileSize); err != nil {
 		return nil, err
 	}
 
-	// 构建映射
-	b, err := syscall.Mmap(int(fd.Fd()), 0, DefaultMemMapSize, syscall.PROT_WRITE|syscall.PROT_READ, syscall.MAP_SHARED)
+	// Building mappings between memory and disk files
+	b, err := syscall.Mmap(int(fd.Fd()), 0, int(fileSize), syscall.PROT_WRITE|syscall.PROT_READ, syscall.MAP_SHARED)
 	if err != nil {
 		return nil, err
 	}
@@ -48,14 +46,16 @@ func NewMMapIOManager(fileName string) (*MMapIO, error) {
 	return mmapIO, nil
 }
 
+// Read Copy data from the mapping area to byte slice
 func (mio *MMapIO) Read(b []byte, offset int64) (int, error) {
 	return copy(b, mio.data[offset:]), nil
 }
 
+// Write Copy data from byte slice to the mapping area
 func (mio *MMapIO) Write(b []byte) (int, error) {
 	oldOffset := mio.offset
 	newOffset := mio.offset + int64(len(b))
-	if newOffset > DefaultMemMapSize {
+	if newOffset > mio.fileSize {
 		return 0, errors.New("exceed file max content length")
 	}
 
@@ -64,6 +64,7 @@ func (mio *MMapIO) Write(b []byte) (int, error) {
 	return copy(mio.data[oldOffset:], b), nil
 }
 
+// Sync Synchronize data from memory to disk
 func (mio *MMapIO) Sync() error {
 	if !mio.dirty {
 		return nil
@@ -78,6 +79,7 @@ func (mio *MMapIO) Sync() error {
 	return nil
 }
 
+// Close file
 func (mio *MMapIO) Close() (err error) {
 	if err = mio.fd.Truncate(mio.offset); err != nil {
 		return err
@@ -91,10 +93,12 @@ func (mio *MMapIO) Close() (err error) {
 	return mio.fd.Close()
 }
 
+// Size return the size of current file
 func (mio *MMapIO) Size() (int64, error) {
 	return mio.offset, nil
 }
 
+// UnMap Unmapping between memory and files
 func (mio *MMapIO) UnMap() error {
 	if mio.data == nil {
 		return nil
diff --git a/fio/mmap_io_test.go b/fio/mmap_io_test.go
index 4d8017ba..82dc4bfd 100644
--- a/fio/mmap_io_test.go
+++ b/fio/mmap_io_test.go
@@ -8,7 +8,7 @@ import (
 
 func TestNewMMapIOManager(t *testing.T) {
 	path := filepath.Join("/tmp", "a.data")
-	mio, err := NewMMapIOManager(path)
+	mio, err := NewMMapIOManager(path, DefaultFileSize)
 	defer destoryFile(path)
 
 	assert.Nil(t, err)
@@ -17,7 +17,7 @@ func TestNewMMapIOManager(t *testing.T) {
 
 func TestMMapIO_Write(t *testing.T) {
 	path := filepath.Join("/tmp", "a.data")
-	mio, err := NewMMapIOManager(path)
+	mio, err := NewMMapIOManager(path, DefaultFileSize)
 	defer destoryFile(path)
 	assert.Nil(t, err)
 	assert.NotNil(t, mio)
@@ -36,7 +36,7 @@ func TestMMapIO_Write(t *testing.T) {
 
 func TestMMapIO_Read(t *testing.T) {
 	path := filepath.Join("/tmp", "a.data")
-	mio, err := NewMMapIOManager(path)
+	mio, err := NewMMapIOManager(path, DefaultFileSize)
 	defer destoryFile(path)
 
 	assert.Nil(t, err)
@@ -60,7 +60,7 @@ func TestMMapIO_Read(t *testing.T) {
 
 func TestMMapIO_Sync(t *testing.T) {
 	path := filepath.Join("/tmp", "a.data")
-	mio, err := NewMMapIOManager(path)
+	mio, err := NewMMapIOManager(path, DefaultFileSize)
 	defer destoryFile(path)
 
 	assert.Nil(t, err)
@@ -73,7 +73,7 @@ func TestMMapIO_Sync(t *testing.T) {
 
 func TestMMapIO_Close(t *testing.T) {
 	path := filepath.Join("/tmp", "a.data")
-	mio, err := NewMMapIOManager(path)
+	mio, err := NewMMapIOManager(path, DefaultFileSize)
 	defer destoryFile(path)
 
 	assert.Nil(t, err)
@@ -88,7 +88,7 @@ func TestMMapIO_Close(t *testing.T) {
 
 func TestMMapIO_Write_Speed(t *testing.T) {
 	path := filepath.Join("/tmp", "a.data")
-	mio, err := NewMMapIOManager(path)
+	mio, err := NewMMapIOManager(path, DefaultFileSize)
 	assert.Nil(t, err)
 	assert.NotNil(t, mio)
 
@@ -104,7 +104,7 @@ func TestMMapIO_Write_Speed(t *testing.T) {
 
 func TestMMapIO_Read_Speed(t *testing.T) {
 	path := filepath.Join("/tmp", "a.data")
-	mio, err := NewMMapIOManager(path)
+	mio, err := NewMMapIOManager(path, DefaultFileSize)
 	defer destoryFile(path)
 	assert.Nil(t, err)
 	assert.NotNil(t, mio)
diff --git a/http/http_server_test.go b/http/http_server_test.go
index c41cf9c6..5f746ab2 100644
--- a/http/http_server_test.go
+++ b/http/http_server_test.go
@@ -38,6 +38,7 @@ func TestNewHTTPServer(t *testing.T) {
 // 测试Put方法
 func TestPut(t *testing.T) {
 	handler, _ := newHttpHandler()
+	defer handler.Close()
 	// 创建一个测试用的http server
 	server := httptest.NewServer(http.HandlerFunc(handler.PutHandler))
 	defer server.Close()
@@ -91,6 +92,7 @@ func TestPut(t *testing.T) {
 
 func TestDel(t *testing.T) {
 	handler, _ := newHttpHandler()
+	defer handler.Close()
 	// 创建一个测试用的http server
 	server := httptest.NewServer(http.HandlerFunc(handler.DelHandler))
 	defer server.Close()
@@ -138,6 +140,7 @@ func TestDel(t *testing.T) {
 
 func TestGet(t *testing.T) {
 	handler, _ := newHttpHandler()
+	defer handler.Close()
 	// 创建一个测试用的http server
 	server := httptest.NewServer(http.HandlerFunc(handler.GetHandler))
 	defer server.Close()
@@ -184,6 +187,7 @@ func TestGet(t *testing.T) {
 
 func TestPost(t *testing.T) {
 	handler, _ := newHttpHandler()
+	defer handler.Close()
 	// 创建一个测试用的 HTTP 服务器
 	server := httptest.NewServer(http.HandlerFunc(handler.PostHandler))
 	defer server.Close()
@@ -238,6 +242,7 @@ func TestPost(t *testing.T) {
 
 func TestGetListKeysHandler(t *testing.T) {
 	handler, _ := newHttpHandler()
+	defer handler.Close()
 	// 创建一个测试用的http server
 	server := httptest.NewServer(http.HandlerFunc(handler.GetListKeysHandler))
 	defer server.Close()
diff --git a/raft/raft.go b/raft/raft.go
index 5d0bf28b..8f31fc9d 100644
--- a/raft/raft.go
+++ b/raft/raft.go
@@ -23,6 +23,7 @@ var DefaultOptions = config.Options{
 	DataFileSize: 256 * 1024 * 1024, // 256MB
 	SyncWrite:    false,
 	IndexType:    Btree,
+	FIOType:      config.FileIOType,
 }
 
 // Cluster define the cluster of db