diff --git a/ecstore/src/disk.rs b/ecstore/src/disk.rs
index 96b7fc99..3309017a 100644
--- a/ecstore/src/disk.rs
+++ b/ecstore/src/disk.rs
@@ -20,9 +20,11 @@ use uuid::Uuid;
 
 use crate::{
     disk_api::{
-        DeleteOptions, DiskAPI, DiskError, FileWriter, ReadMultipleReq, ReadMultipleResp, ReadOptions, RenameDataResp, VolumeInfo,
+        DeleteOptions, DiskAPI, DiskError, FileReader, FileWriter, ReadMultipleReq, ReadMultipleResp, ReadOptions,
+        RenameDataResp, VolumeInfo,
     },
     endpoint::{Endpoint, Endpoints},
+    erasure::ReadAt,
     file_meta::FileMeta,
     format::FormatV3,
     store_api::{FileInfo, RawFileInfo},
@@ -505,19 +507,21 @@ impl DiskAPI for LocalDisk {
 
         // Ok(())
     }
-    async fn read_file(&self, volume: &str, path: &str, offset: usize, length: usize) -> Result<(Vec<u8>, usize)> {
+    async fn read_file(&self, volume: &str, path: &str) -> Result<FileReader> {
         let p = self.get_object_path(&volume, &path)?;
-        let mut file = File::options().read(true).open(&p).await?;
+        let file = File::options().read(true).open(&p).await?;
 
-        file.seek(SeekFrom::Start(offset as u64)).await?;
+        Ok(FileReader::new(file))
 
-        let mut buffer = vec![0; length];
+        // file.seek(SeekFrom::Start(offset as u64)).await?;
 
-        let bytes_read = file.read(&mut buffer).await?;
+        // let mut buffer = vec![0; length];
 
-        buffer.truncate(bytes_read);
+        // let bytes_read = file.read(&mut buffer).await?;
 
-        Ok((buffer, bytes_read))
+        // buffer.truncate(bytes_read);
+
+        // Ok((buffer, bytes_read))
     }
     async fn rename_data(
         &self,
diff --git a/ecstore/src/disk_api.rs b/ecstore/src/disk_api.rs
index 69b55498..c5b4b135 100644
--- a/ecstore/src/disk_api.rs
+++ b/ecstore/src/disk_api.rs
@@ -1,12 +1,18 @@
-use std::{fmt::Debug, pin::Pin};
+use std::{fmt::Debug, io::SeekFrom, pin::Pin};
 
 use anyhow::{Error, Result};
 use bytes::Bytes;
 use time::OffsetDateTime;
-use tokio::io::AsyncWrite;
+use tokio::{
+    fs::File,
+    io::{AsyncRead, AsyncReadExt, AsyncSeekExt, AsyncWrite},
+};
 use uuid::Uuid;
 
-use crate::store_api::{FileInfo, RawFileInfo};
+use crate::{
+    erasure::ReadAt,
+    store_api::{FileInfo, RawFileInfo},
+};
 
 #[async_trait::async_trait]
 pub trait DiskAPI: Debug + Send + Sync + 'static {
@@ -19,7 +25,7 @@ pub trait DiskAPI: Debug + Send + Sync + 'static {
     async fn rename_file(&self, src_volume: &str, src_path: &str, dst_volume: &str, dst_path: &str) -> Result<()>;
     async fn create_file(&self, origvolume: &str, volume: &str, path: &str, file_size: usize) -> Result<FileWriter>;
     async fn append_file(&self, volume: &str, path: &str) -> Result<FileWriter>;
-    async fn read_file(&self, volume: &str, path: &str, offset: usize, length: usize) -> Result<(Vec<u8>, usize)>;
+    async fn read_file(&self, volume: &str, path: &str) -> Result<FileReader>;
     async fn rename_data(
         &self,
         src_volume: &str,
@@ -139,6 +145,30 @@ impl FileWriter {
     }
 }
 
+pub struct FileReader {
+    pub inner: File,
+}
+
+impl FileReader {
+    pub fn new(inner: File) -> Self {
+        Self { inner }
+    }
+}
+
+impl ReadAt for FileReader {
+    async fn read_at(&mut self, offset: usize, length: usize) -> Result<(Vec<u8>, usize)> {
+        self.inner.seek(SeekFrom::Start(offset as u64)).await?;
+
+        let mut buffer = vec![0; length];
+
+        let bytes_read = self.inner.read(&mut buffer).await?;
+
+        buffer.truncate(bytes_read);
+
+        Ok((buffer, bytes_read))
+    }
+}
+
 #[derive(Debug, thiserror::Error)]
 pub enum DiskError {
     #[error("file not found")]
diff --git a/ecstore/src/erasure.rs b/ecstore/src/erasure.rs
index fb82cc8b..b3a715af 100644
--- a/ecstore/src/erasure.rs
+++ b/ecstore/src/erasure.rs
@@ -1,8 +1,11 @@
 use anyhow::anyhow;
+use anyhow::Error;
 use anyhow::Result;
 use bytes::Bytes;
+use futures::future::join_all;
 use futures::{Stream, StreamExt};
 use reed_solomon_erasure::galois_8::ReedSolomon;
+use s3s::dto::StreamingBlob;
 use s3s::StdError;
 use tokio::io::AsyncWrite;
 use tokio::io::AsyncWriteExt;
@@ -10,10 +13,12 @@ use tokio::io::AsyncWriteExt;
 use uuid::Uuid;
 
 use crate::chunk_stream::ChunkedStream;
+use crate::disk_api::DiskError;
+use crate::disk_api::FileReader;
 
 pub struct Erasure {
-    // data_shards: usize,
-    // parity_shards: usize,
+    data_shards: usize,
+    parity_shards: usize,
     encoder: ReedSolomon,
     block_size: usize,
     id: Uuid,
@@ -22,8 +27,8 @@ pub struct Erasure {
 impl Erasure {
     pub fn new(data_shards: usize, parity_shards: usize, block_size: usize) -> Self {
         Erasure {
-            // data_shards,
-            // parity_shards,
+            data_shards,
+            parity_shards,
             block_size,
             encoder: ReedSolomon::new(data_shards, parity_shards).unwrap(),
             id: Uuid::new_v4(),
@@ -35,23 +40,23 @@ impl Erasure {
         body: S,
         writers: &mut Vec<W>,
         // block_size: usize,
-        data_size: usize,
+        total_size: usize,
         _write_quorum: usize,
     ) -> Result<usize>
     where
         S: Stream<Item = Result<Bytes, StdError>> + Send + Sync + 'static,
         W: AsyncWrite + Unpin,
     {
-        let mut stream = ChunkedStream::new(body, data_size, self.block_size, true);
+        let mut stream = ChunkedStream::new(body, total_size, self.block_size, true);
         let mut total: usize = 0;
-        let mut idx = 0;
+        // let mut idx = 0;
         while let Some(result) = stream.next().await {
             match result {
                 Ok(data) => {
                     let blocks = self.encode_data(data.as_ref())?;
 
                     let mut errs = Vec::new();
-                    idx += 1;
+                    // idx += 1;
                     for (i, w) in writers.iter_mut().enumerate() {
                         total += blocks[i].len();
 
@@ -95,31 +100,74 @@ impl Erasure {
         // }
     }
 
-    pub async fn decode<R, W>(&self, writer: W, readers: Vec<R>, offset: usize, length: usize, total_length: usize) -> Result<()>
-    where
-        R: ReadAt,
-        W: AsyncWrite + Unpin,
-    {
+    pub async fn decode(
+        &self,
+        writer: &StreamingBlob,
+        readers: Vec<Option<FileReader>>,
+        offset: usize,
+        length: usize,
+        total_length: usize,
+    ) -> Result<usize> {
+        if length == 0 {
+            return Ok(0);
+        }
+
+        let mut reader = ShardReader::new(readers, self, offset, total_length);
+
+        let start_block = offset / self.block_size;
+        let end_block = (offset + length) / self.block_size;
+
+        for block_idx in start_block..=end_block {
+            let mut block_offset = 0;
+            let mut block_length = 0;
+            if start_block == end_block {
+                block_offset = offset % self.block_size;
+                block_length = length;
+            } else if block_idx == start_block {
+                block_offset = offset % self.block_size;
+                block_length = self.block_size - block_offset;
+            } else if block_idx == end_block {
+                block_offset = 0;
+                block_length = (offset + length) % self.block_size;
+            } else {
+                block_offset = 0;
+                block_length = self.block_size;
+            }
+
+            if block_length == 0 {
+                break;
+            }
+
+            let mut bufs = reader.read().await?;
+
+            self.decode_data(&mut bufs)?;
+        }
+        unimplemented!()
+    }
+
+    fn write_data_blocks() -> Result<()> {
         unimplemented!()
     }
 
     pub fn encode_data(&self, data: &[u8]) -> Result<Vec<Vec<u8>>> {
         let (shard_size, total_size) = self.need_size(data.len());
 
+        // 生成一个新的 所需的所有分片数据长度
         let mut data_buffer = vec![0u8; total_size];
         {
+            // 复制源数据
             let (left, _) = data_buffer.split_at_mut(data.len());
             left.copy_from_slice(data);
         }
 
         {
+            // ec encode, 结果会写进 data_buffer
             let data_slices: Vec<&mut [u8]> = data_buffer.chunks_mut(shard_size).collect();
 
             self.encoder.encode(data_slices)?;
         }
 
-        // Ok(data_buffer)
-
+        // 分片
         let mut shards = Vec::with_capacity(self.encoder.total_shard_count());
 
         let slices: Vec<&[u8]> = data_buffer.chunks(shard_size).collect();
@@ -142,22 +190,97 @@ impl Erasure {
         (shard_size, shard_size * (self.encoder.total_shard_count()))
     }
 
+    // 算出每个分片大小
     fn shard_size(&self, data_size: usize) -> usize {
         (data_size + self.encoder.data_shard_count() - 1) / self.encoder.data_shard_count()
     }
+    // returns final erasure size from original size.
+    fn shard_file_size(&self, total_size: usize) -> usize {
+        if total_size == 0 {
+            return 0;
+        }
+
+        let mut num_shards = total_size / self.block_size;
+        let last_block_size = total_size % self.block_size;
+        // let last_shard_size = (last_block_size + self.data_shards - 1) / self.data_shards;
+        // num_shards * self.shard_size(self.block_size) + last_shard_size
+
+        // 因为写入的时候ec需要补全，所以最后一个长度应该也是一样的
+        if last_block_size != 0 {
+            num_shards += 1
+        }
+        num_shards * self.shard_size(self.block_size)
+    }
 }
 
 pub trait ReadAt {
-    async fn read_at(&self, volume: &str, path: &str, offset: usize, length: usize) -> Result<(Vec<u8>, usize)>;
+    async fn read_at(&mut self, offset: usize, length: usize) -> Result<(Vec<u8>, usize)>;
 }
 
-pub struct ShardReader<R> {
-    readers: Vec<R>,
+pub struct ShardReader {
+    readers: Vec<Option<FileReader>>, // 磁盘
+    data_block_count: usize,          // 总的分片数量
+    shard_size: usize,                // 每个分片的块大小 一次读取一块
+    shard_file_size: usize,           // 分片文件总长度
+    offset: usize,                    // 在分片中的offset
 }
 
-impl<R: ReadAt> ShardReader<R> {
-    pub fn new(readers: Vec<R>, offset: usize, total_length: usize) -> Self {
-        Self { readers }
+impl ShardReader {
+    pub fn new(readers: Vec<Option<FileReader>>, ec: &Erasure, offset: usize, total_length: usize) -> Self {
+        Self {
+            readers,
+            data_block_count: ec.encoder.data_shard_count(),
+            shard_size: ec.shard_size(ec.block_size),
+            shard_file_size: ec.shard_file_size(total_length),
+            offset: (offset / ec.block_size) * ec.shard_size(ec.block_size),
+        }
+    }
+
+    pub async fn read(&mut self) -> Result<Vec<Option<Vec<u8>>>> {
+        // let mut disks = self.readers;
+
+        let reader_length = self.readers.len();
+
+        let mut futures = Vec::with_capacity(reader_length);
+        let mut errors = Vec::with_capacity(reader_length);
+
+        let mut ress = Vec::with_capacity(reader_length);
+
+        for disk in self.readers.iter_mut() {
+            if disk.is_none() {
+                ress.push(None);
+                errors.push(Some(Error::new(DiskError::DiskNotFound)));
+                continue;
+            }
+
+            let disk: &mut FileReader = disk.as_mut().unwrap();
+            futures.push(disk.read_at(self.offset, self.shard_size));
+        }
+
+        let results = join_all(futures).await;
+        for result in results {
+            match result {
+                Ok((res, _)) => {
+                    ress.push(Some(res));
+                    errors.push(None);
+                }
+                Err(e) => {
+                    ress.push(None);
+                    errors.push(Some(e));
+                }
+            }
+        }
+
+        if !self.can_decode(&ress) {
+            return Err(Error::msg("shard reader read faild"));
+        }
+
+        self.offset += self.shard_size;
+
+        Ok(ress)
+    }
+    fn can_decode(&self, bufs: &Vec<Option<Vec<u8>>>) -> bool {
+        bufs.iter().filter(|v| v.is_some()).count() > self.data_block_count
     }
 }