diff --git a/erasure-appendfile.go b/erasure-appendfile.go
index 449633f0e..d604fc0d9 100644
--- a/erasure-appendfile.go
+++ b/erasure-appendfile.go
@@ -19,16 +19,16 @@ package main
 import "sync"
 
 // AppendFile - append data buffer at path.
-func (e erasure) AppendFile(volume, path string, dataBuffer []byte) (n int64, err error) {
+func (e erasureConfig) AppendFile(volume, path string, dataBuffer []byte) (n int64, err error) {
 	// Split the input buffer into data and parity blocks.
 	var blocks [][]byte
-	blocks, err = e.ReedSolomon.Split(dataBuffer)
+	blocks, err = e.reedSolomon.Split(dataBuffer)
 	if err != nil {
 		return 0, err
 	}
 
 	// Encode parity blocks using data blocks.
-	err = e.ReedSolomon.Encode(blocks)
+	err = e.reedSolomon.Encode(blocks)
 	if err != nil {
 		return 0, err
 	}
@@ -55,6 +55,10 @@ func (e erasure) AppendFile(volume, path string, dataBuffer []byte) (n int64, er
 				wErrs[index] = errUnexpected
 				return
 			}
+			// Calculate hash.
+			e.hashWriters[blockIndex].Write(blocks[blockIndex])
+
+			// Successfully wrote.
 			wErrs[index] = nil
 		}(index, disk)
 	}
diff --git a/erasure-readfile.go b/erasure-readfile.go
index 84fd2d255..0f088cd1b 100644
--- a/erasure-readfile.go
+++ b/erasure-readfile.go
@@ -16,82 +16,136 @@
 
 package main
 
-import "errors"
+import (
+	"encoding/hex"
+	"errors"
+)
+
+// isValidBlock - calculates the checksum hash for the block and
+// validates if its correct returns true for valid cases, false otherwise.
+func (e erasureConfig) isValidBlock(volume, path string, blockIdx int) bool {
+	diskIndex := -1
+	// Find out the right disk index for the input block index.
+	for index, blockIndex := range e.distribution {
+		if blockIndex == blockIdx {
+			diskIndex = index
+		}
+	}
+	// Unknown block index requested, treat it as error.
+	if diskIndex == -1 {
+		return false
+	}
+	// Disk is not present, treat entire block to be non existent.
+	if e.storageDisks[diskIndex] == nil {
+		return false
+	}
+	// Read everything for a given block and calculate hash.
+	hashBytes, err := hashSum(e.storageDisks[diskIndex], volume, path, newHash(e.checkSumAlgo))
+	if err != nil {
+		return false
+	}
+	return hex.EncodeToString(hashBytes) == e.hashChecksums[diskIndex]
+}
 
 // ReadFile - decoded erasure coded file.
-func (e erasure) ReadFile(volume, path string, startOffset int64, buffer []byte) (int64, error) {
-	// Calculate the current encoded block size.
-	curEncBlockSize := getEncodedBlockLen(int64(len(buffer)), e.DataBlocks)
-	offsetEncOffset := getEncodedBlockLen(startOffset, e.DataBlocks)
+func (e erasureConfig) ReadFile(volume, path string, size int64, blockSize int64) ([]byte, error) {
+	// Return data buffer.
+	var buffer []byte
 
-	// Allocate encoded blocks up to storage disks.
-	enBlocks := make([][]byte, len(e.storageDisks))
+	// Total size left
+	totalSizeLeft := size
 
-	// Counter to keep success data blocks.
-	var successDataBlocksCount = 0
-	var noReconstruct bool // Set for no reconstruction.
+	// Starting offset for reading.
+	startOffset := int64(0)
 
-	// Read from all the disks.
-	for index, disk := range e.storageDisks {
-		blockIndex := e.distribution[index] - 1
-		if disk == nil {
-			continue
+	// Write until each parts are read and exhausted.
+	for totalSizeLeft > 0 {
+		// Calculate the proper block size.
+		var curBlockSize int64
+		if blockSize < totalSizeLeft {
+			curBlockSize = blockSize
+		} else {
+			curBlockSize = totalSizeLeft
 		}
-		// Initialize shard slice and fill the data from each parts.
-		enBlocks[blockIndex] = make([]byte, curEncBlockSize)
-		// Read the necessary blocks.
-		_, err := disk.ReadFile(volume, path, offsetEncOffset, enBlocks[blockIndex])
-		if err != nil {
-			enBlocks[blockIndex] = nil
-		}
-		// Verify if we have successfully read all the data blocks.
-		if blockIndex < e.DataBlocks && enBlocks[blockIndex] != nil {
-			successDataBlocksCount++
-			// Set when we have all the data blocks and no
-			// reconstruction is needed, so that we can avoid
-			// erasure reconstruction.
-			noReconstruct = successDataBlocksCount == e.DataBlocks
-			if noReconstruct {
-				// Break out we have read all the data blocks.
-				break
+
+		// Calculate the current encoded block size.
+		curEncBlockSize := getEncodedBlockLen(curBlockSize, e.dataBlocks)
+		offsetEncOffset := getEncodedBlockLen(startOffset, e.dataBlocks)
+
+		// Allocate encoded blocks up to storage disks.
+		enBlocks := make([][]byte, len(e.storageDisks))
+
+		// Counter to keep success data blocks.
+		var successDataBlocksCount = 0
+		var noReconstruct bool // Set for no reconstruction.
+
+		// Read from all the disks.
+		for index, disk := range e.storageDisks {
+			blockIndex := e.distribution[index] - 1
+			if !e.isValidBlock(volume, path, blockIndex) {
+				continue
+			}
+			// Initialize shard slice and fill the data from each parts.
+			enBlocks[blockIndex] = make([]byte, curEncBlockSize)
+			// Read the necessary blocks.
+			_, err := disk.ReadFile(volume, path, offsetEncOffset, enBlocks[blockIndex])
+			if err != nil {
+				enBlocks[blockIndex] = nil
+			}
+			// Verify if we have successfully read all the data blocks.
+			if blockIndex < e.dataBlocks && enBlocks[blockIndex] != nil {
+				successDataBlocksCount++
+				// Set when we have all the data blocks and no
+				// reconstruction is needed, so that we can avoid
+				// erasure reconstruction.
+				noReconstruct = successDataBlocksCount == e.dataBlocks
+				if noReconstruct {
+					// Break out we have read all the data blocks.
+					break
+				}
 			}
 		}
-	}
 
-	// Check blocks if they are all zero in length, we have corruption return error.
-	if checkBlockSize(enBlocks) == 0 {
-		return 0, errDataCorrupt
-	}
+		// Check blocks if they are all zero in length, we have corruption return error.
+		if checkBlockSize(enBlocks) == 0 {
+			return nil, errDataCorrupt
+		}
 
-	// Verify if reconstruction is needed, proceed with reconstruction.
-	if !noReconstruct {
-		err := e.ReedSolomon.Reconstruct(enBlocks)
+		// Verify if reconstruction is needed, proceed with reconstruction.
+		if !noReconstruct {
+			err := e.reedSolomon.Reconstruct(enBlocks)
+			if err != nil {
+				return nil, err
+			}
+			// Verify reconstructed blocks (parity).
+			ok, err := e.reedSolomon.Verify(enBlocks)
+			if err != nil {
+				return nil, err
+			}
+			if !ok {
+				// Blocks cannot be reconstructed, corrupted data.
+				err = errors.New("Verification failed after reconstruction, data likely corrupted.")
+				return nil, err
+			}
+		}
+
+		// Get data blocks from encoded blocks.
+		dataBlocks, err := getDataBlocks(enBlocks, e.dataBlocks, int(curBlockSize))
 		if err != nil {
-			return 0, err
-		}
-		// Verify reconstructed blocks (parity).
-		ok, err := e.ReedSolomon.Verify(enBlocks)
-		if err != nil {
-			return 0, err
-		}
-		if !ok {
-			// Blocks cannot be reconstructed, corrupted data.
-			err = errors.New("Verification failed after reconstruction, data likely corrupted.")
-			return 0, err
+			return nil, err
 		}
+
+		// Copy data blocks.
+		buffer = append(buffer, dataBlocks...)
+
+		// Negate the 'n' size written to client.
+		totalSizeLeft -= int64(len(dataBlocks))
+
+		// Increase the offset to move forward.
+		startOffset += int64(len(dataBlocks))
+
+		// Relenquish memory.
+		dataBlocks = nil
 	}
-
-	// Get data blocks from encoded blocks.
-	dataBlocks, err := getDataBlocks(enBlocks, e.DataBlocks, len(buffer))
-	if err != nil {
-		return 0, err
-	}
-
-	// Copy data blocks.
-	copy(buffer, dataBlocks)
-
-	// Relenquish memory.
-	dataBlocks = nil
-
-	return int64(len(buffer)), nil
+	return buffer, nil
 }
diff --git a/erasure-utils.go b/erasure-utils.go
index 86dca895a..625e7f314 100644
--- a/erasure-utils.go
+++ b/erasure-utils.go
@@ -16,7 +16,42 @@
 
 package main
 
-import "github.com/klauspost/reedsolomon"
+import (
+	"crypto/sha512"
+	"hash"
+	"io"
+
+	"github.com/klauspost/reedsolomon"
+)
+
+// newHash - gives you a newly allocated hash depending on the input algorithm.
+func newHash(algo string) hash.Hash {
+	switch algo {
+	case "sha512":
+		return sha512.New()
+	// Add new hashes here.
+	default:
+		return sha512.New()
+	}
+}
+
+func hashSum(disk StorageAPI, volume, path string, writer hash.Hash) ([]byte, error) {
+	startOffset := int64(0)
+	// Read until io.EOF.
+	for {
+		buf := make([]byte, blockSizeV1)
+		n, err := disk.ReadFile(volume, path, startOffset, buf)
+		if err == io.EOF {
+			break
+		}
+		if err != nil && err != io.EOF {
+			return nil, err
+		}
+		writer.Write(buf[:n])
+		startOffset += n
+	}
+	return writer.Sum(nil), nil
+}
 
 // getDataBlocks - fetches the data block only part of the input encoded blocks.
 func getDataBlocks(enBlocks [][]byte, dataBlocks int, curBlockSize int) (data []byte, err error) {
@@ -31,6 +66,7 @@ func getDataBlocks(enBlocks [][]byte, dataBlocks int, curBlockSize int) (data []
 	if size < curBlockSize {
 		return nil, reedsolomon.ErrShortData
 	}
+
 	write := curBlockSize
 	for _, block := range blocks {
 		if write < len(block) {
diff --git a/erasure.go b/erasure.go
index 80d9c6769..980ede8dc 100644
--- a/erasure.go
+++ b/erasure.go
@@ -16,21 +16,30 @@
 
 package main
 
-import "github.com/klauspost/reedsolomon"
+import (
+	"encoding/hex"
+	"hash"
+
+	"github.com/klauspost/reedsolomon"
+)
 
 // erasure storage layer.
-type erasure struct {
-	ReedSolomon  reedsolomon.Encoder // Erasure encoder/decoder.
-	DataBlocks   int
-	ParityBlocks int
-	storageDisks []StorageAPI
-	distribution []int
+type erasureConfig struct {
+	reedSolomon  reedsolomon.Encoder // Erasure encoder/decoder.
+	dataBlocks   int                 // Calculated data disks.
+	storageDisks []StorageAPI        // Initialized storage disks.
+	distribution []int               // Erasure block distribution.
+	hashWriters  []hash.Hash         // Allocate hash writers.
+
+	// Carries hex checksums needed for validating Reads.
+	hashChecksums []string
+	checkSumAlgo  string
 }
 
 // newErasure instantiate a new erasure.
-func newErasure(disks []StorageAPI, distribution []int) *erasure {
+func newErasure(disks []StorageAPI, distribution []int) *erasureConfig {
 	// Initialize E.
-	e := &erasure{}
+	e := &erasureConfig{}
 
 	// Calculate data and parity blocks.
 	dataBlocks, parityBlocks := len(disks)/2, len(disks)/2
@@ -40,9 +49,8 @@ func newErasure(disks []StorageAPI, distribution []int) *erasure {
 	fatalIf(err, "Unable to initialize reedsolomon package.")
 
 	// Save the reedsolomon.
-	e.DataBlocks = dataBlocks
-	e.ParityBlocks = parityBlocks
-	e.ReedSolomon = rs
+	e.dataBlocks = dataBlocks
+	e.reedSolomon = rs
 
 	// Save all the initialized storage disks.
 	e.storageDisks = disks
@@ -53,3 +61,31 @@ func newErasure(disks []StorageAPI, distribution []int) *erasure {
 	// Return successfully initialized.
 	return e
 }
+
+// SaveAlgo - FIXME.
+func (e *erasureConfig) SaveAlgo(algo string) {
+	e.checkSumAlgo = algo
+}
+
+// Save hex encoded hashes - saves hashes that need to be validated
+// during reads for each blocks.
+func (e *erasureConfig) SaveHashes(hashes []string) {
+	e.hashChecksums = hashes
+}
+
+// InitHash - initializes new hash for all blocks.
+func (e *erasureConfig) InitHash(algo string) {
+	e.hashWriters = make([]hash.Hash, len(e.storageDisks))
+	for index := range e.storageDisks {
+		e.hashWriters[index] = newHash(algo)
+	}
+}
+
+// GetHashes - returns a slice of hex encoded hash.
+func (e erasureConfig) GetHashes() []string {
+	var hexHashes = make([]string, len(e.storageDisks))
+	for index, hashWriter := range e.hashWriters {
+		hexHashes[index] = hex.EncodeToString(hashWriter.Sum(nil))
+	}
+	return hexHashes
+}
diff --git a/fs-v1-metadata.go b/fs-v1-metadata.go
index b37252900..94e7c3610 100644
--- a/fs-v1-metadata.go
+++ b/fs-v1-metadata.go
@@ -52,7 +52,7 @@ func (m *fsMetaV1) AddObjectPart(partNumber int, partName string, partETag strin
 	m.Parts = append(m.Parts, partInfo)
 
 	// Parts in fsMeta should be in sorted order by part number.
-	sort.Sort(byPartNumber(m.Parts))
+	sort.Sort(byObjectPartNumber(m.Parts))
 }
 
 // readFSMetadata - returns the object metadata `fs.json` content.
diff --git a/xl-v1-healing.go b/xl-v1-healing.go
index b29feaed3..a77cd102e 100644
--- a/xl-v1-healing.go
+++ b/xl-v1-healing.go
@@ -41,19 +41,18 @@ func (xl xlObjects) readAllXLMetadata(bucket, object string) ([]xlMetaV1, []erro
 		wg.Add(1)
 		go func(index int, disk StorageAPI) {
 			defer wg.Done()
-			offset := int64(0)
-			var buffer = make([]byte, blockSizeV1)
-			n, err := disk.ReadFile(bucket, xlMetaPath, offset, buffer)
+			buffer, err := readAll(disk, bucket, xlMetaPath)
 			if err != nil {
 				errs[index] = err
 				return
 			}
-			err = json.Unmarshal(buffer[:n], &metadataArray[index])
+			err = json.Unmarshal(buffer, &metadataArray[index])
 			if err != nil {
 				// Unable to parse xl.json, set error.
 				errs[index] = err
 				return
 			}
+			// Relinquish buffer.
 			buffer = nil
 			errs[index] = nil
 		}(index, disk)
@@ -151,9 +150,8 @@ func (xl xlObjects) shouldHeal(onlineDisks []StorageAPI) (heal bool) {
 // - xlMetaV1
 // - bool value indicating if healing is needed.
 // - error if any.
-func (xl xlObjects) listOnlineDisks(bucket, object string) (onlineDisks []StorageAPI, version int64, err error) {
+func (xl xlObjects) listOnlineDisks(partsMetadata []xlMetaV1, errs []error) (onlineDisks []StorageAPI, version int64, err error) {
 	onlineDisks = make([]StorageAPI, len(xl.storageDisks))
-	partsMetadata, errs := xl.readAllXLMetadata(bucket, object)
 	if err = xl.reduceError(errs); err != nil {
 		if err == errFileNotFound {
 			// For file not found, treat as if disks are available
diff --git a/xl-v1-metadata.go b/xl-v1-metadata.go
index 844599eb5..d676893f0 100644
--- a/xl-v1-metadata.go
+++ b/xl-v1-metadata.go
@@ -18,6 +18,7 @@ package main
 
 import (
 	"encoding/json"
+	"fmt"
 	"path"
 	"sort"
 	"sync"
@@ -39,12 +40,19 @@ type objectPartInfo struct {
 	Size   int64  `json:"size"`
 }
 
-// byPartName is a collection satisfying sort.Interface.
-type byPartNumber []objectPartInfo
+// byObjectPartNumber is a collection satisfying sort.Interface.
+type byObjectPartNumber []objectPartInfo
 
-func (t byPartNumber) Len() int           { return len(t) }
-func (t byPartNumber) Swap(i, j int)      { t[i], t[j] = t[j], t[i] }
-func (t byPartNumber) Less(i, j int) bool { return t[i].Number < t[j].Number }
+func (t byObjectPartNumber) Len() int           { return len(t) }
+func (t byObjectPartNumber) Swap(i, j int)      { t[i], t[j] = t[j], t[i] }
+func (t byObjectPartNumber) Less(i, j int) bool { return t[i].Number < t[j].Number }
+
+// checkSumInfo - carries checksums of individual part.
+type checkSumInfo struct {
+	Name      string `json:"name"`
+	Algorithm string `json:"algorithm"`
+	Hash      string `json:"hash"`
+}
 
 // A xlMetaV1 represents a metadata header mapping keys to sets of values.
 type xlMetaV1 struct {
@@ -56,17 +64,13 @@ type xlMetaV1 struct {
 		Version int64     `json:"version"`
 	} `json:"stat"`
 	Erasure struct {
-		Algorithm    string `json:"algorithm"`
-		DataBlocks   int    `json:"data"`
-		ParityBlocks int    `json:"parity"`
-		BlockSize    int64  `json:"blockSize"`
-		Index        int    `json:"index"`
-		Distribution []int  `json:"distribution"`
-		Checksum     []struct {
-			Name      string `json:"name"`
-			Algorithm string `json:"algorithm"`
-			Hash      string `json:"hash"`
-		} `json:"checksum"`
+		Algorithm    string         `json:"algorithm"`
+		DataBlocks   int            `json:"data"`
+		ParityBlocks int            `json:"parity"`
+		BlockSize    int64          `json:"blockSize"`
+		Index        int            `json:"index"`
+		Distribution []int          `json:"distribution"`
+		Checksum     []checkSumInfo `json:"checksum,omitempty"`
 	} `json:"erasure"`
 	Minio struct {
 		Release string `json:"release"`
@@ -89,6 +93,11 @@ func newXLMetaV1(dataBlocks, parityBlocks int) (xlMeta xlMetaV1) {
 	return xlMeta
 }
 
+// IsValid - is validate tells if the format is sane.
+func (m xlMetaV1) IsValid() bool {
+	return m.Version == "1" && m.Format == "xl"
+}
+
 // ObjectPartIndex - returns the index of matching object part number.
 func (m xlMetaV1) ObjectPartIndex(partNumber int) (index int) {
 	for i, part := range m.Parts {
@@ -100,6 +109,17 @@ func (m xlMetaV1) ObjectPartIndex(partNumber int) (index int) {
 	return -1
 }
 
+// ObjectCheckIndex - returns the checksum for the part name from the checksum slice.
+func (m xlMetaV1) PartObjectChecksum(partNumber int) checkSumInfo {
+	partName := fmt.Sprintf("object%d", partNumber)
+	for _, checksum := range m.Erasure.Checksum {
+		if checksum.Name == partName {
+			return checksum
+		}
+	}
+	return checkSumInfo{}
+}
+
 // AddObjectPart - add a new object part in order.
 func (m *xlMetaV1) AddObjectPart(partNumber int, partName string, partETag string, partSize int64) {
 	partInfo := objectPartInfo{
@@ -121,11 +141,11 @@ func (m *xlMetaV1) AddObjectPart(partNumber int, partName string, partETag strin
 	m.Parts = append(m.Parts, partInfo)
 
 	// Parts in xlMeta should be in sorted order by part number.
-	sort.Sort(byPartNumber(m.Parts))
+	sort.Sort(byObjectPartNumber(m.Parts))
 }
 
-// objectToPartOffset - translate offset of an object to offset of its individual part.
-func (m xlMetaV1) objectToPartOffset(offset int64) (partIndex int, partOffset int64, err error) {
+// ObjectToPartOffset - translate offset of an object to offset of its individual part.
+func (m xlMetaV1) ObjectToPartOffset(offset int64) (partIndex int, partOffset int64, err error) {
 	partOffset = offset
 	// Seek until object offset maps to a particular part offset.
 	for i, part := range m.Parts {
@@ -146,6 +166,18 @@ func (m xlMetaV1) objectToPartOffset(offset int64) (partIndex int, partOffset in
 	return 0, 0, InvalidRange{}
 }
 
+// pickValidXLMeta - picks one valid xlMeta content and returns from a
+// slice of xlmeta content. If no value is found this function panics
+// and dies.
+func pickValidXLMeta(xlMetas []xlMetaV1) xlMetaV1 {
+	for _, xlMeta := range xlMetas {
+		if xlMeta.IsValid() {
+			return xlMeta
+		}
+	}
+	panic("Unable to look for valid XL metadata content")
+}
+
 // readXLMetadata - returns the object metadata `xl.json` content from
 // one of the disks picked at random.
 func (xl xlObjects) readXLMetadata(bucket, object string) (xlMeta xlMetaV1, err error) {
@@ -160,7 +192,10 @@ func (xl xlObjects) readXLMetadata(bucket, object string) (xlMeta xlMetaV1, err
 		if err == nil {
 			err = json.Unmarshal(buffer, &xlMeta)
 			if err == nil {
-				return xlMeta, nil
+				if xlMeta.IsValid() {
+					return xlMeta, nil
+				}
+				err = errDataCorrupt
 			}
 		}
 		xlJSONErrCount++ // Update error count.
@@ -209,12 +244,85 @@ func (xl xlObjects) renameXLMetadata(srcBucket, srcPrefix, dstBucket, dstPrefix
 	return nil
 }
 
+// writeXLMetadata - writes `xl.json` to a single disk.
+func writeXLMetadata(disk StorageAPI, bucket, prefix string, xlMeta xlMetaV1) error {
+	jsonFile := path.Join(prefix, xlMetaJSONFile)
+
+	// Marshal json.
+	metadataBytes, err := json.Marshal(&xlMeta)
+	if err != nil {
+		return err
+	}
+	// Persist marshalled data.
+	n, err := disk.AppendFile(bucket, jsonFile, metadataBytes)
+	if err != nil {
+		return err
+	}
+	if n != int64(len(metadataBytes)) {
+		return errUnexpected
+	}
+	return nil
+}
+
+// checkSumAlgorithm - get the algorithm required for checksum
+// verification for a given part. Allocates a new hash and returns.
+func checkSumAlgorithm(xlMeta xlMetaV1, partIdx int) string {
+	partCheckSumInfo := xlMeta.PartObjectChecksum(partIdx)
+	return partCheckSumInfo.Algorithm
+}
+
+// xlMetaPartBlockChecksums - get block checksums for a given part.
+func (xl xlObjects) metaPartBlockChecksums(xlMetas []xlMetaV1, partIdx int) (blockCheckSums []string) {
+	for index := range xl.storageDisks {
+		// Save the read checksums for a given part.
+		blockCheckSums = append(blockCheckSums, xlMetas[index].PartObjectChecksum(partIdx).Hash)
+	}
+	return blockCheckSums
+}
+
+// writeUniqueXLMetadata - writes unique `xl.json` content for each disk in order.
+func (xl xlObjects) writeUniqueXLMetadata(bucket, prefix string, xlMetas []xlMetaV1) error {
+	var wg = &sync.WaitGroup{}
+	var mErrs = make([]error, len(xl.storageDisks))
+
+	// Start writing `xl.json` to all disks in parallel.
+	for index, disk := range xl.storageDisks {
+		wg.Add(1)
+		// Write `xl.json` in a routine.
+		go func(index int, disk StorageAPI) {
+			defer wg.Done()
+
+			// Pick one xlMeta for a disk at index.
+			xlMetas[index].Erasure.Index = index + 1
+
+			// Write unique `xl.json` for a disk at index.
+			if err := writeXLMetadata(disk, bucket, prefix, xlMetas[index]); err != nil {
+				mErrs[index] = err
+				return
+			}
+			mErrs[index] = nil
+		}(index, disk)
+	}
+
+	// Wait for all the routines.
+	wg.Wait()
+
+	// Return the first error.
+	for _, err := range mErrs {
+		if err == nil {
+			continue
+		}
+		return err
+	}
+
+	return nil
+}
+
 // writeXLMetadata - write `xl.json` on all disks in order.
 func (xl xlObjects) writeXLMetadata(bucket, prefix string, xlMeta xlMetaV1) error {
 	var wg = &sync.WaitGroup{}
 	var mErrs = make([]error, len(xl.storageDisks))
 
-	jsonFile := path.Join(prefix, xlMetaJSONFile)
 	// Start writing `xl.json` to all disks in parallel.
 	for index, disk := range xl.storageDisks {
 		wg.Add(1)
@@ -225,21 +333,11 @@ func (xl xlObjects) writeXLMetadata(bucket, prefix string, xlMeta xlMetaV1) erro
 			// Save the disk order index.
 			metadata.Erasure.Index = index + 1
 
-			metadataBytes, err := json.Marshal(&metadata)
-			if err != nil {
+			// Write xl metadata.
+			if err := writeXLMetadata(disk, bucket, prefix, metadata); err != nil {
 				mErrs[index] = err
 				return
 			}
-			// Persist marshalled data.
-			n, mErr := disk.AppendFile(bucket, jsonFile, metadataBytes)
-			if mErr != nil {
-				mErrs[index] = mErr
-				return
-			}
-			if n != int64(len(metadataBytes)) {
-				mErrs[index] = errUnexpected
-				return
-			}
 			mErrs[index] = nil
 		}(index, disk, xlMeta)
 	}
diff --git a/xl-v1-multipart.go b/xl-v1-multipart.go
index 96a1a145b..597aa65fd 100644
--- a/xl-v1-multipart.go
+++ b/xl-v1-multipart.go
@@ -110,39 +110,32 @@ func (xl xlObjects) putObjectPart(bucket string, object string, uploadID string,
 	if !IsValidObjectName(object) {
 		return "", ObjectNameInvalid{Bucket: bucket, Object: object}
 	}
-	uploadIDLocked := false
-	defer func() {
-		if uploadIDLocked {
-			nsMutex.Unlock(minioMetaBucket, pathJoin(mpartMetaPrefix, bucket, object, uploadID))
-		}
-	}()
-	// Figure out the erasure distribution first.
-	nsMutex.Lock(minioMetaBucket, pathJoin(mpartMetaPrefix, bucket, object, uploadID))
-	uploadIDLocked = true
+	uploadIDPath := pathJoin(mpartMetaPrefix, bucket, object, uploadID)
+	nsMutex.Lock(minioMetaBucket, uploadIDPath)
+	defer nsMutex.Unlock(minioMetaBucket, uploadIDPath)
 
 	if !xl.isUploadIDExists(bucket, object, uploadID) {
 		return "", InvalidUploadID{UploadID: uploadID}
 	}
 
-	uploadIDPath := path.Join(mpartMetaPrefix, bucket, object, uploadID)
-	xlMeta, err := xl.readXLMetadata(minioMetaBucket, uploadIDPath)
-	if err != nil {
-		return "", toObjectErr(err, minioMetaBucket, uploadIDPath)
-	}
+	// Read metadata associated with the object from all disks.
+	partsMetadata, errs := xl.readAllXLMetadata(minioMetaBucket, uploadIDPath)
 
 	// List all online disks.
-	onlineDisks, higherVersion, err := xl.listOnlineDisks(minioMetaBucket, pathJoin(mpartMetaPrefix, bucket, object, uploadID))
+	onlineDisks, higherVersion, err := xl.listOnlineDisks(partsMetadata, errs)
 	if err != nil {
 		return "", toObjectErr(err, bucket, object)
 	}
 
-	// Unlock the uploadID so that parallel uploads of parts can happen.
-	nsMutex.Unlock(minioMetaBucket, pathJoin(mpartMetaPrefix, bucket, object, uploadID))
-	uploadIDLocked = false
+	// Pick one from the first valid metadata.
+	xlMeta := pickValidXLMeta(partsMetadata)
 
 	// Initialize a new erasure with online disks and new distribution.
 	erasure := newErasure(onlineDisks, xlMeta.Erasure.Distribution)
 
+	// Initialize sha512 hash.
+	erasure.InitHash("sha512")
+
 	partSuffix := fmt.Sprintf("object%d", partID)
 	tmpPartPath := path.Join(tmpMetaPrefix, uploadID, partSuffix)
 
@@ -182,31 +175,12 @@ func (xl xlObjects) putObjectPart(bucket string, object string, uploadID string,
 		}
 	}
 
-	// Hold lock as we are updating UPLODID/xl.json and renaming the part file from tmp location.
-	nsMutex.Lock(minioMetaBucket, pathJoin(mpartMetaPrefix, bucket, object, uploadID))
-	uploadIDLocked = true
-
 	if !xl.isUploadIDExists(bucket, object, uploadID) {
 		return "", InvalidUploadID{UploadID: uploadID}
 	}
 
-	// List all online disks.
-	onlineDisks, higherVersion, err = xl.listOnlineDisks(minioMetaBucket, pathJoin(mpartMetaPrefix, bucket, object, uploadID))
-	if err != nil {
-		return "", toObjectErr(err, bucket, object)
-	}
-
-	// Increment version only if we have online disks less than configured storage disks.
-	if diskCount(onlineDisks) < len(xl.storageDisks) {
-		higherVersion++
-	}
-
-	xlMeta, err = xl.readXLMetadata(minioMetaBucket, uploadIDPath)
-	if err != nil {
-		return "", toObjectErr(err, minioMetaBucket, uploadIDPath)
-	}
 	// Rename temporary part file to its final location.
-	partPath := path.Join(mpartMetaPrefix, bucket, object, uploadID, partSuffix)
+	partPath := path.Join(uploadIDPath, partSuffix)
 	err = xl.renameObject(minioMetaBucket, tmpPartPath, minioMetaBucket, partPath)
 	if err != nil {
 		return "", toObjectErr(err, minioMetaBucket, partPath)
@@ -214,10 +188,32 @@ func (xl xlObjects) putObjectPart(bucket string, object string, uploadID string,
 
 	// Once part is successfully committed, proceed with updating XL metadata.
 	xlMeta.Stat.Version = higherVersion
+	// Add the current part.
 	xlMeta.AddObjectPart(partID, partSuffix, newMD5Hex, size)
 
+	// Get calculated hash checksums from erasure to save in `xl.json`.
+	hashChecksums := erasure.GetHashes()
+
+	checkSums := make([]checkSumInfo, len(xl.storageDisks))
+	for index := range xl.storageDisks {
+		blockIndex := xlMeta.Erasure.Distribution[index] - 1
+		checkSums[blockIndex] = checkSumInfo{
+			Name:      partSuffix,
+			Algorithm: "sha512",
+			Hash:      hashChecksums[blockIndex],
+		}
+	}
+	for index := range partsMetadata {
+		blockIndex := xlMeta.Erasure.Distribution[index] - 1
+		partsMetadata[index].Parts = xlMeta.Parts
+		partsMetadata[index].Erasure.Checksum = append(partsMetadata[index].Erasure.Checksum, checkSums[blockIndex])
+	}
+
+	// Write all the checksum metadata.
 	tempUploadIDPath := path.Join(tmpMetaPrefix, uploadID)
-	if err = xl.writeXLMetadata(minioMetaBucket, tempUploadIDPath, xlMeta); err != nil {
+
+	// Write unique `xl.json` each disk.
+	if err = xl.writeUniqueXLMetadata(minioMetaBucket, tempUploadIDPath, partsMetadata); err != nil {
 		return "", toObjectErr(err, minioMetaBucket, tempUploadIDPath)
 	}
 	rErr := xl.renameXLMetadata(minioMetaBucket, tempUploadIDPath, minioMetaBucket, uploadIDPath)
@@ -258,6 +254,7 @@ func (xl xlObjects) listObjectParts(bucket, object, uploadID string, partNumberM
 	result := ListPartsInfo{}
 
 	uploadIDPath := path.Join(mpartMetaPrefix, bucket, object, uploadID)
+
 	xlMeta, err := xl.readXLMetadata(minioMetaBucket, uploadIDPath)
 	if err != nil {
 		return ListPartsInfo{}, toObjectErr(err, minioMetaBucket, uploadIDPath)
@@ -352,14 +349,18 @@ func (xl xlObjects) CompleteMultipartUpload(bucket string, object string, upload
 
 	uploadIDPath := pathJoin(mpartMetaPrefix, bucket, object, uploadID)
 
-	// Read the current `xl.json`.
-	xlMeta, err := xl.readXLMetadata(minioMetaBucket, uploadIDPath)
-	if err != nil {
+	// Read metadata associated with the object from all disks.
+	partsMetadata, errs := xl.readAllXLMetadata(minioMetaBucket, uploadIDPath)
+	if err = xl.reduceError(errs); err != nil {
 		return "", toObjectErr(err, minioMetaBucket, uploadIDPath)
 	}
 
+	// Calculate full object size.
 	var objectSize int64
 
+	// Pick one from the first valid metadata.
+	xlMeta := pickValidXLMeta(partsMetadata)
+
 	// Save current xl meta for validation.
 	var currentXLMeta = xlMeta
 
@@ -405,7 +406,16 @@ func (xl xlObjects) CompleteMultipartUpload(bucket string, object string, upload
 	xlMeta.Meta["md5Sum"] = s3MD5
 	uploadIDPath = path.Join(mpartMetaPrefix, bucket, object, uploadID)
 	tempUploadIDPath := path.Join(tmpMetaPrefix, uploadID)
-	if err = xl.writeXLMetadata(minioMetaBucket, tempUploadIDPath, xlMeta); err != nil {
+
+	// Update all xl metadata, make sure to not modify fields like
+	// checksum which are different on each disks.
+	for index := range partsMetadata {
+		partsMetadata[index].Stat = xlMeta.Stat
+		partsMetadata[index].Meta = xlMeta.Meta
+		partsMetadata[index].Parts = xlMeta.Parts
+	}
+	// Write unique `xl.json` for each disk.
+	if err = xl.writeUniqueXLMetadata(minioMetaBucket, tempUploadIDPath, partsMetadata); err != nil {
 		return "", toObjectErr(err, minioMetaBucket, tempUploadIDPath)
 	}
 	rErr := xl.renameXLMetadata(minioMetaBucket, tempUploadIDPath, minioMetaBucket, uploadIDPath)
diff --git a/xl-v1-object.go b/xl-v1-object.go
index 3fc9ef889..684850e50 100644
--- a/xl-v1-object.go
+++ b/xl-v1-object.go
@@ -31,63 +31,83 @@ func (xl xlObjects) GetObject(bucket, object string, startOffset int64, length i
 	nsMutex.RLock(bucket, object)
 	defer nsMutex.RUnlock(bucket, object)
 
-	// Read metadata associated with the object.
-	xlMeta, err := xl.readXLMetadata(bucket, object)
-	if err != nil {
+	// Read metadata associated with the object from all disks.
+	partsMetadata, errs := xl.readAllXLMetadata(bucket, object)
+	if err := xl.reduceError(errs); err != nil {
 		return toObjectErr(err, bucket, object)
 	}
 
 	// List all online disks.
-	onlineDisks, _, err := xl.listOnlineDisks(bucket, object)
+	onlineDisks, _, err := xl.listOnlineDisks(partsMetadata, errs)
 	if err != nil {
 		return toObjectErr(err, bucket, object)
 	}
 
-	// Initialize a new erasure with online disks, with previous block distribution.
-	erasure := newErasure(onlineDisks, xlMeta.Erasure.Distribution)
+	// Pick one from the first valid metadata.
+	xlMeta := partsMetadata[0]
+	if !xlMeta.IsValid() {
+		for _, partMetadata := range partsMetadata {
+			if partMetadata.IsValid() {
+				xlMeta = partMetadata
+				break
+			}
+		}
+	}
 
 	// Get part index offset.
-	partIndex, partOffset, err := xlMeta.objectToPartOffset(startOffset)
+	partIndex, partOffset, err := xlMeta.ObjectToPartOffset(startOffset)
 	if err != nil {
 		return toObjectErr(err, bucket, object)
 	}
+
+	// Read from all parts.
 	for ; partIndex < len(xlMeta.Parts); partIndex++ {
-		part := xlMeta.Parts[partIndex]
-		totalLeft := part.Size
-		beginOffset := int64(0)
-		for totalLeft > 0 {
-			var curBlockSize int64
-			if xlMeta.Erasure.BlockSize < totalLeft {
-				curBlockSize = xlMeta.Erasure.BlockSize
-			} else {
-				curBlockSize = totalLeft
-			}
-			var buffer = make([]byte, curBlockSize)
-			var n int64
-			n, err = erasure.ReadFile(bucket, pathJoin(object, part.Name), beginOffset, buffer)
+		// Save the current part name and size.
+		partName := xlMeta.Parts[partIndex].Name
+		partSize := xlMeta.Parts[partIndex].Size
+
+		// Initialize a new erasure with online disks, with previous
+		// block distribution for each part reads.
+		erasure := newErasure(onlineDisks, xlMeta.Erasure.Distribution)
+
+		// Set previously calculated block checksums and algorithm for validation.
+		erasure.SaveAlgo(checkSumAlgorithm(xlMeta, partIndex+1))
+		erasure.SaveHashes(xl.metaPartBlockChecksums(partsMetadata, partIndex+1))
+
+		// Data block size.
+		blockSize := xlMeta.Erasure.BlockSize
+
+		// Start reading the part name.
+		var buffer []byte
+		buffer, err = erasure.ReadFile(bucket, pathJoin(object, partName), partSize, blockSize)
+		if err != nil {
+			return err
+		}
+
+		// Copy to client until length requested.
+		if length > int64(len(buffer)) {
+			var m int64
+			m, err = io.Copy(writer, bytes.NewReader(buffer[partOffset:]))
 			if err != nil {
 				return err
 			}
-			if length > int64(len(buffer)) {
-				var m int64
-				m, err = io.Copy(writer, bytes.NewReader(buffer[partOffset:]))
-				if err != nil {
-					return err
-				}
-				length -= m
-			} else {
-				_, err = io.CopyN(writer, bytes.NewReader(buffer[partOffset:]), length)
-				if err != nil {
-					return err
-				}
-				return nil
+			length -= m
+		} else {
+			_, err = io.CopyN(writer, bytes.NewReader(buffer[partOffset:]), length)
+			if err != nil {
+				return err
 			}
-			totalLeft -= n
-			beginOffset += n
-			// Reset part offset to 0 to read rest of the part from the beginning.
-			partOffset = 0
+			return nil
 		}
+
+		// Relinquish memory.
+		buffer = nil
+
+		// Reset part offset to 0 to read rest of the part from the beginning.
+		partOffset = 0
 	}
+
+	// Return success.
 	return nil
 }
 
@@ -220,8 +240,11 @@ func (xl xlObjects) PutObject(bucket string, object string, size int64, data io.
 	// Initialize xl meta.
 	xlMeta := newXLMetaV1(xl.dataBlocks, xl.parityBlocks)
 
+	// Read metadata associated with the object from all disks.
+	partsMetadata, errs := xl.readAllXLMetadata(bucket, object)
+
 	// List all online disks.
-	onlineDisks, higherVersion, err := xl.listOnlineDisks(bucket, object)
+	onlineDisks, higherVersion, err := xl.listOnlineDisks(partsMetadata, errs)
 	if err != nil {
 		return "", toObjectErr(err, bucket, object)
 	}
@@ -234,6 +257,9 @@ func (xl xlObjects) PutObject(bucket string, object string, size int64, data io.
 	// Initialize a new erasure with online disks and new distribution.
 	erasure := newErasure(onlineDisks, xlMeta.Erasure.Distribution)
 
+	// Initialize sha512 hash.
+	erasure.InitHash("sha512")
+
 	// Initialize md5 writer.
 	md5Writer := md5.New()
 
@@ -305,10 +331,33 @@ func (xl xlObjects) PutObject(bucket string, object string, size int64, data io.
 	xlMeta.Stat.Size = size
 	xlMeta.Stat.ModTime = modTime
 	xlMeta.Stat.Version = higherVersion
+	// Add the final part.
 	xlMeta.AddObjectPart(1, "object1", newMD5Hex, xlMeta.Stat.Size)
 
-	// Write `xl.json` metadata.
-	if err = xl.writeXLMetadata(minioMetaBucket, tempObj, xlMeta); err != nil {
+	// Get hash checksums.
+	hashChecksums := erasure.GetHashes()
+
+	// Save the checksums.
+	checkSums := make([]checkSumInfo, len(xl.storageDisks))
+	for index := range xl.storageDisks {
+		blockIndex := xlMeta.Erasure.Distribution[index] - 1
+		checkSums[blockIndex] = checkSumInfo{
+			Name:      "object1",
+			Algorithm: "sha512",
+			Hash:      hashChecksums[blockIndex],
+		}
+	}
+
+	// Update all the necessary fields making sure that checkSum field
+	// is different for each disks.
+	for index := range partsMetadata {
+		blockIndex := xlMeta.Erasure.Distribution[index] - 1
+		partsMetadata[index] = xlMeta
+		partsMetadata[index].Erasure.Checksum = append(partsMetadata[index].Erasure.Checksum, checkSums[blockIndex])
+	}
+
+	// Write unique `xl.json` for each disk.
+	if err = xl.writeUniqueXLMetadata(minioMetaBucket, tempObj, partsMetadata); err != nil {
 		return "", toObjectErr(err, bucket, object)
 	}