xl: Change fileMetadata to xlMetadata. (#1404)

Finalized backend format

```
{
    "version": "1.0.0",
    "stat": {
        "size": 24256,
        "modTime": "2016-04-28T00:11:37.843Z"
    },
    "erasure": {
        "data": 5,
        "parity": 5,
        "blockSize": 4194304
    ],
    "minio": {
        "release": "RELEASE.2016-04-28T00-09-47Z"
    }
}
```

xl-json.md

@@ -0,0 +1,39 @@
+### xl.json
+
+``xl.json`` is a special file captured and written by XL storage API layer
+to interpret, manage and extract erasured data to multiple disks.
+
+```json
+{
+    "version": "1.0.0",
+    "stat": {
+        "size": 24256,
+        "modTime": "2016-04-28T00:11:37.843Z",
+        "version": 0
+    },
+    "erasure": {
+        "data": 5,
+        "parity": 5,
+        "blockSize": 4194304
+    ],
+    "minio": {
+        "release": "RELEASE.2016-04-28T00-09-47Z"
+    }
+}
+```
+
+#### JSON meaning.
+
+- "version" // Version of the meta json file.
+
+- "stat" // Stat value of written file.
+
+  - "size"     // Size of the file.
+  - "modTime"  // Modified time of the file.
+  - "version"  // File version tracked when disks are down.
+
+- "erasure" // Erasure metadata for the written file.
+
+  - "data"       // Data blocks parts of the file.
+  - "parity"     // Parity blocks parts of the file.
+  - "blockSize"  // BlockSize read/write chunk size.

xl-v1-common.go

@@ -17,7 +17,6 @@
 package main
 
 import (
-	"encoding/json"
 	"errors"
 	slashpath "path"
 	"path/filepath"
@@ -37,27 +36,11 @@ func highestInt(intSlice []int64) (highestInteger int64) {
 }
 
 // Extracts file versions from partsMetadata slice and returns version slice.
-func listFileVersions(partsMetadata []fileMetadata, errs []error) (versions []int64, err error) {
+func listFileVersions(partsMetadata []xlMetaV1, errs []error) (versions []int64, err error) {
 	versions = make([]int64, len(partsMetadata))
 	for index, metadata := range partsMetadata {
 		if errs[index] == nil {
-			var version int64
-			version, err = metadata.GetFileVersion()
-			if err == errMetadataKeyNotExist {
-				log.WithFields(logrus.Fields{
-					"metadata": metadata,
-				}).Errorf("Missing 'file.version', %s", errMetadataKeyNotExist)
-				versions[index] = 0
-				continue
-			}
-			if err != nil {
-				log.WithFields(logrus.Fields{
-					"metadata": metadata,
-				}).Errorf("'file.version' decoding failed with %s", err)
-				// Unexpected, return error.
-				return nil, err
-			}
-			versions[index] = version
+			versions[index] = metadata.Stat.Version
 		} else {
 			versions[index] = -1
 		}
@@ -67,10 +50,10 @@ func listFileVersions(partsMetadata []fileMetadata, errs []error) (versions []in
 
 // Returns slice of online disks needed.
 // - slice returing readable disks.
-// - fileMetadata
+// - xlMetaV1
 // - bool value indicating if healing is needed.
 // - error if any.
-func (xl XL) listOnlineDisks(volume, path string) (onlineDisks []StorageAPI, mdata fileMetadata, heal bool, err error) {
+func (xl XL) listOnlineDisks(volume, path string) (onlineDisks []StorageAPI, mdata xlMetaV1, heal bool, err error) {
 	partsMetadata, errs := xl.getPartsMetadata(volume, path)
 	notFoundCount := 0
 	// FIXME: take care of the situation when a disk has failed and been removed
@@ -82,8 +65,8 @@ func (xl XL) listOnlineDisks(volume, path string) (onlineDisks []StorageAPI, mda
 			notFoundCount++
 			// If we have errors with file not found greater than allowed read
 			// quorum we return err as errFileNotFound.
-			if notFoundCount > xl.readQuorum {
-				return nil, fileMetadata{}, false, errFileNotFound
+			if notFoundCount > len(xl.storageDisks)-xl.readQuorum {
+				return nil, xlMetaV1{}, false, errFileNotFound
 			}
 		}
 	}
@@ -96,7 +79,7 @@ func (xl XL) listOnlineDisks(volume, path string) (onlineDisks []StorageAPI, mda
 			"volume": volume,
 			"path":   path,
 		}).Errorf("Extracting file versions failed with %s", err)
-		return nil, fileMetadata{}, false, err
+		return nil, xlMetaV1{}, false, err
 	}
 
 	// Get highest file version.
@@ -130,31 +113,31 @@ func (xl XL) listOnlineDisks(volume, path string) (onlineDisks []StorageAPI, mda
 				"onlineDiskCount": onlineDiskCount,
 				"readQuorumCount": xl.readQuorum,
 			}).Errorf("%s", errReadQuorum)
-			return nil, fileMetadata{}, false, errReadQuorum
+			return nil, xlMetaV1{}, false, errReadQuorum
 		}
 	}
 	return onlineDisks, mdata, heal, nil
 }
 
-// Get parts.json metadata as a map slice.
+// Get xl.json metadata as a map slice.
 // Returns error slice indicating the failed metadata reads.
 // Read lockNS() should be done by caller.
-func (xl XL) getPartsMetadata(volume, path string) ([]fileMetadata, []error) {
+func (xl XL) getPartsMetadata(volume, path string) ([]xlMetaV1, []error) {
 	errs := make([]error, len(xl.storageDisks))
-	metadataArray := make([]fileMetadata, len(xl.storageDisks))
-	metadataFilePath := slashpath.Join(path, metadataFile)
+	metadataArray := make([]xlMetaV1, len(xl.storageDisks))
+	xlMetaV1FilePath := slashpath.Join(path, xlMetaV1File)
 	for index, disk := range xl.storageDisks {
 		offset := int64(0)
-		metadataReader, err := disk.ReadFile(volume, metadataFilePath, offset)
+		metadataReader, err := disk.ReadFile(volume, xlMetaV1FilePath, offset)
 		if err != nil {
 			errs[index] = err
 			continue
 		}
 		defer metadataReader.Close()
 
-		metadata, err := fileMetadataDecode(metadataReader)
+		metadata, err := xlMetaV1Decode(metadataReader)
 		if err != nil {
-			// Unable to parse parts.json, set error.
+			// Unable to parse xl.json, set error.
 			errs[index] = err
 			continue
 		}
@@ -163,38 +146,30 @@ func (xl XL) getPartsMetadata(volume, path string) ([]fileMetadata, []error) {
 	return metadataArray, errs
 }
 
-// Writes/Updates `parts.json` for given file. updateParts carries
-// index of disks where `parts.json` needs to be updated.
+// Writes/Updates `xl.json` for given file. updateParts carries
+// index of disks where `xl.json` needs to be updated.
 //
 // Returns collection of errors, indexed in accordance with input
 // updateParts order.
 // Write lockNS() should be done by caller.
-func (xl XL) setPartsMetadata(volume, path string, metadata fileMetadata, updateParts []bool) []error {
-	metadataFilePath := filepath.Join(path, metadataFile)
+func (xl XL) setPartsMetadata(volume, path string, metadata xlMetaV1, updateParts []bool) []error {
+	xlMetaV1FilePath := filepath.Join(path, xlMetaV1File)
 	errs := make([]error, len(xl.storageDisks))
 
 	for index := range updateParts {
 		errs[index] = errors.New("Metadata not updated")
 	}
 
-	metadataBytes, err := json.Marshal(metadata)
-	if err != nil {
-		for index := range updateParts {
-			errs[index] = err
-		}
-		return errs
-	}
-
 	for index, shouldUpdate := range updateParts {
 		if !shouldUpdate {
 			continue
 		}
-		writer, err := xl.storageDisks[index].CreateFile(volume, metadataFilePath)
+		writer, err := xl.storageDisks[index].CreateFile(volume, xlMetaV1FilePath)
 		errs[index] = err
 		if err != nil {
 			continue
 		}
-		_, err = writer.Write(metadataBytes)
+		err = metadata.Write(writer)
 		if err != nil {
 			errs[index] = err
 			safeCloseAndRemove(writer)

xl-v1-createfile.go

@@ -17,16 +17,12 @@
 package main
 
 import (
-	"encoding/hex"
 	"fmt"
-	"hash"
 	"io"
 	slashpath "path"
-	"strconv"
 	"time"
 
 	"github.com/Sirupsen/logrus"
-	fastSha512 "github.com/minio/minio/pkg/crypto/sha512"
 )
 
 // Erasure block size.
@@ -92,9 +88,8 @@ func (xl XL) writeErasure(volume, path string, reader *io.PipeReader, wcloser *w
 	higherVersion++
 
 	writers := make([]io.WriteCloser, len(xl.storageDisks))
-	sha512Writers := make([]hash.Hash, len(xl.storageDisks))
 
-	metadataFilePath := slashpath.Join(path, metadataFile)
+	xlMetaV1FilePath := slashpath.Join(path, xlMetaV1File)
 	metadataWriters := make([]io.WriteCloser, len(xl.storageDisks))
 
 	// Save additional erasureMetadata.
@@ -102,7 +97,7 @@ func (xl XL) writeErasure(volume, path string, reader *io.PipeReader, wcloser *w
 
 	createFileError := 0
 	for index, disk := range xl.storageDisks {
-		erasurePart := slashpath.Join(path, fmt.Sprintf("part.%d", index))
+		erasurePart := slashpath.Join(path, fmt.Sprintf("file.%d", index))
 		var writer io.WriteCloser
 		writer, err = disk.CreateFile(volume, erasurePart)
 		if err != nil {
@@ -126,7 +121,7 @@ func (xl XL) writeErasure(volume, path string, reader *io.PipeReader, wcloser *w
 
 		// create meta data file
 		var metadataWriter io.WriteCloser
-		metadataWriter, err = disk.CreateFile(volume, metadataFilePath)
+		metadataWriter, err = disk.CreateFile(volume, xlMetaV1FilePath)
 		if err != nil {
 			log.WithFields(logrus.Fields{
 				"volume": volume,
@@ -148,7 +143,6 @@ func (xl XL) writeErasure(volume, path string, reader *io.PipeReader, wcloser *w
 
 		writers[index] = writer
 		metadataWriters[index] = metadataWriter
-		sha512Writers[index] = fastSha512.New()
 	}
 
 	// Allocate 4MiB block size buffer for reading.
@@ -221,9 +215,6 @@ func (xl XL) writeErasure(volume, path string, reader *io.PipeReader, wcloser *w
 					reader.CloseWithError(err)
 					return
 				}
-				if sha512Writers[index] != nil {
-					sha512Writers[index].Write(encodedData)
-				}
 			}
 
 			// Update total written.
@@ -232,21 +223,19 @@ func (xl XL) writeErasure(volume, path string, reader *io.PipeReader, wcloser *w
 	}
 
 	// Initialize metadata map, save all erasure related metadata.
-	metadata := make(fileMetadata)
-	metadata.Set("version", minioVersion)
-	metadata.Set("format.major", "1")
-	metadata.Set("format.minor", "0")
-	metadata.Set("format.patch", "0")
-	metadata.Set("file.size", strconv.FormatInt(totalSize, 10))
+	metadata := xlMetaV1{}
+	metadata.Version = "1"
+	metadata.Stat.Size = totalSize
+	metadata.Stat.ModTime = modTime
+	metadata.Minio.Release = minioReleaseTag
 	if len(xl.storageDisks) > len(writers) {
 		// Save file.version only if we wrote to less disks than all
 		// storage disks.
-		metadata.Set("file.version", strconv.FormatInt(higherVersion, 10))
+		metadata.Stat.Version = higherVersion
 	}
-	metadata.Set("file.modTime", modTime.Format(timeFormatAMZ))
-	metadata.Set("file.xl.blockSize", strconv.Itoa(erasureBlockSize))
-	metadata.Set("file.xl.dataBlocks", strconv.Itoa(xl.DataBlocks))
-	metadata.Set("file.xl.parityBlocks", strconv.Itoa(xl.ParityBlocks))
+	metadata.Erasure.DataBlocks = xl.DataBlocks
+	metadata.Erasure.ParityBlocks = xl.ParityBlocks
+	metadata.Erasure.BlockSize = erasureBlockSize
 
 	// Write all the metadata.
 	// below case is not handled here
@@ -257,10 +246,6 @@ func (xl XL) writeErasure(volume, path string, reader *io.PipeReader, wcloser *w
 		if metadataWriter == nil {
 			continue
 		}
-		if sha512Writers[index] != nil {
-			// Save sha512 checksum of each encoded blocks.
-			metadata.Set("file.xl.block512Sum", hex.EncodeToString(sha512Writers[index].Sum(nil)))
-		}
 
 		// Write metadata.
 		err = metadata.Write(metadataWriter)

xl-v1-healfile.go

@@ -50,21 +50,12 @@ func (xl XL) healFile(volume string, path string) error {
 		return nil
 	}
 
-	size, err := metadata.GetSize()
-	if err != nil {
-		log.WithFields(logrus.Fields{
-			"volume": volume,
-			"path":   path,
-		}).Errorf("Failed to get file size, %s", err)
-		return err
-	}
-
 	for index, disk := range onlineDisks {
 		if disk == nil {
 			needsHeal[index] = true
 			continue
 		}
-		erasurePart := slashpath.Join(path, fmt.Sprintf("part.%d", index))
+		erasurePart := slashpath.Join(path, fmt.Sprintf("file.%d", index))
 		// If disk.ReadFile returns error and we don't have read quorum it will be taken care as
 		// ReedSolomon.Reconstruct() will fail later.
 		var reader io.ReadCloser
@@ -93,7 +84,7 @@ func (xl XL) healFile(volume string, path string) error {
 		if !healNeeded {
 			continue
 		}
-		erasurePart := slashpath.Join(path, fmt.Sprintf("part.%d", index))
+		erasurePart := slashpath.Join(path, fmt.Sprintf("file.%d", index))
 		writers[index], err = xl.storageDisks[index].CreateFile(volume, erasurePart)
 		if err != nil {
 			log.WithFields(logrus.Fields{
@@ -105,17 +96,17 @@ func (xl XL) healFile(volume string, path string) error {
 			return err
 		}
 	}
-	var totalLeft = size
+	var totalLeft = metadata.Stat.Size
 	for totalLeft > 0 {
 		// Figure out the right blockSize.
-		var curBlockSize int
-		if erasureBlockSize < totalLeft {
-			curBlockSize = erasureBlockSize
+		var curBlockSize int64
+		if metadata.Erasure.BlockSize < totalLeft {
+			curBlockSize = metadata.Erasure.BlockSize
 		} else {
-			curBlockSize = int(totalLeft)
+			curBlockSize = totalLeft
 		}
 		// Calculate the current block size.
-		curBlockSize = getEncodedBlockLen(curBlockSize, xl.DataBlocks)
+		curBlockSize = getEncodedBlockLen(curBlockSize, metadata.Erasure.DataBlocks)
 		enBlocks := make([][]byte, totalBlocks)
 		// Loop through all readers and read.
 		for index, reader := range readers {
@@ -205,7 +196,7 @@ func (xl XL) healFile(volume string, path string) error {
 				return err
 			}
 		}
-		totalLeft = totalLeft - erasureBlockSize
+		totalLeft = totalLeft - metadata.Erasure.BlockSize
 	}
 
 	// After successful healing Close() the writer so that the temp

xl-v1-metadata.go

@@ -18,53 +18,31 @@ package main
 
 import (
 	"encoding/json"
-	"errors"
 	"io"
-	"strconv"
 	"time"
 )
 
-// error type when key is not found.
-var errMetadataKeyNotExist = errors.New("Key not found in fileMetadata.")
-
-// This code is built on similar ideas of http.Header.
-// Ref - https://golang.org/pkg/net/http/#Header
-
-// A fileMetadata represents a metadata header mapping
-// keys to sets of values.
-type fileMetadata map[string][]string
-
-// Add adds the key, value pair to the header.
-// It appends to any existing values associated with key.
-func (f fileMetadata) Add(key, value string) {
-	f[key] = append(f[key], value)
-}
-
-// Set sets the header entries associated with key to
-// the single element value. It replaces any existing
-// values associated with key.
-func (f fileMetadata) Set(key, value string) {
-	f[key] = []string{value}
-}
-
-// Get gets the first value associated with the given key.
-// If there are no values associated with the key, Get returns "".
-// Get is a convenience method.  For more complex queries,
-// access the map directly.
-func (f fileMetadata) Get(key string) []string {
-	if f == nil {
-		return nil
+// A xlMetaV1 represents a metadata header mapping keys to sets of values.
+type xlMetaV1 struct {
+	Version string `json:"version"`
+	Stat    struct {
+		Size    int64     `json:"size"`
+		ModTime time.Time `json:"modTime"`
+		Version int64     `json:"version"`
+	} `json:"stat"`
+	Erasure struct {
+		DataBlocks   int   `json:"data"`
+		ParityBlocks int   `json:"parity"`
+		BlockSize    int64 `json:"blockSize"`
 	}
-	v, ok := f[key]
-	if !ok {
-		return nil
-	}
-	return v
+	Minio struct {
+		Release string `json:"release"`
+	} `json:"minio"`
 }
 
 // Write writes a metadata in wire format.
-func (f fileMetadata) Write(writer io.Writer) error {
-	metadataBytes, err := json.Marshal(f)
+func (m xlMetaV1) Write(writer io.Writer) error {
+	metadataBytes, err := json.Marshal(m)
 	if err != nil {
 		return err
 	}
@@ -72,56 +50,12 @@ func (f fileMetadata) Write(writer io.Writer) error {
 	return err
 }
 
-// Get file size.
-func (f fileMetadata) GetSize() (int64, error) {
-	sizes := f.Get("file.size")
-	if sizes == nil {
-		return 0, errMetadataKeyNotExist
-	}
-	sizeStr := sizes[0]
-	return strconv.ParseInt(sizeStr, 10, 64)
-}
-
-// Set file size.
-func (f fileMetadata) SetSize(size int64) {
-	f.Set("file.size", strconv.FormatInt(size, 10))
-}
-
-// Get file Modification time.
-func (f fileMetadata) GetModTime() (time.Time, error) {
-	timeStrs := f.Get("file.modTime")
-	if timeStrs == nil {
-		return time.Time{}, errMetadataKeyNotExist
-	}
-	return time.Parse(timeFormatAMZ, timeStrs[0])
-}
-
-// Set file Modification time.
-func (f fileMetadata) SetModTime(modTime time.Time) {
-	f.Set("file.modTime", modTime.Format(timeFormatAMZ))
-}
-
-// Get file version.
-func (f fileMetadata) GetFileVersion() (int64, error) {
-	version := f.Get("file.version")
-	if version == nil {
-		return 0, errMetadataKeyNotExist
-	}
-	return strconv.ParseInt(version[0], 10, 64)
-}
-
-// Set file version.
-func (f fileMetadata) SetFileVersion(fileVersion int64) {
-	f.Set("file.version", strconv.FormatInt(fileVersion, 10))
-}
-
-// fileMetadataDecode - file metadata decode.
-func fileMetadataDecode(reader io.Reader) (fileMetadata, error) {
-	metadata := make(fileMetadata)
+// xlMetaV1Decode - file metadata decode.
+func xlMetaV1Decode(reader io.Reader) (metadata xlMetaV1, err error) {
 	decoder := json.NewDecoder(reader)
 	// Unmarshalling failed, file possibly corrupted.
-	if err := decoder.Decode(&metadata); err != nil {
-		return nil, err
+	if err = decoder.Decode(&metadata); err != nil {
+		return xlMetaV1{}, err
 	}
 	return metadata, nil
 }

xl-v1-readfile.go

@@ -62,15 +62,6 @@ func (xl XL) ReadFile(volume, path string, offset int64) (io.ReadCloser, error)
 		}()
 	}
 
-	fileSize, err := metadata.GetSize()
-	if err != nil {
-		log.WithFields(logrus.Fields{
-			"volume": volume,
-			"path":   path,
-		}).Errorf("Failed to get file size, %s", err)
-		return nil, err
-	}
-
 	// Acquire read lock again.
 	xl.lockNS(volume, path, readLock)
 	readers := make([]io.ReadCloser, len(xl.storageDisks))
@@ -78,7 +69,7 @@ func (xl XL) ReadFile(volume, path string, offset int64) (io.ReadCloser, error)
 		if disk == nil {
 			continue
 		}
-		erasurePart := slashpath.Join(path, fmt.Sprintf("part.%d", index))
+		erasurePart := slashpath.Join(path, fmt.Sprintf("file.%d", index))
 		// If disk.ReadFile returns error and we don't have read quorum it will be taken care as
 		// ReedSolomon.Reconstruct() will fail later.
 		var reader io.ReadCloser
@@ -91,18 +82,18 @@ func (xl XL) ReadFile(volume, path string, offset int64) (io.ReadCloser, error)
 	// Initialize pipe.
 	pipeReader, pipeWriter := io.Pipe()
 	go func() {
-		var totalLeft = fileSize
+		var totalLeft = metadata.Stat.Size
 		// Read until the totalLeft.
 		for totalLeft > 0 {
 			// Figure out the right blockSize as it was encoded before.
-			var curBlockSize int
-			if erasureBlockSize < totalLeft {
-				curBlockSize = erasureBlockSize
+			var curBlockSize int64
+			if metadata.Erasure.BlockSize < totalLeft {
+				curBlockSize = metadata.Erasure.BlockSize
 			} else {
-				curBlockSize = int(totalLeft)
+				curBlockSize = totalLeft
 			}
 			// Calculate the current encoded block size.
-			curEncBlockSize := getEncodedBlockLen(curBlockSize, xl.DataBlocks)
+			curEncBlockSize := getEncodedBlockLen(curBlockSize, metadata.Erasure.DataBlocks)
 			enBlocks := make([][]byte, len(xl.storageDisks))
 			// Loop through all readers and read.
 			for index, reader := range readers {
@@ -117,8 +108,6 @@ func (xl XL) ReadFile(volume, path string, offset int64) (io.ReadCloser, error)
 				}
 			}
 
-			// TODO need to verify block512Sum.
-
 			// Check blocks if they are all zero in length.
 			if checkBlockSize(enBlocks) == 0 {
 				log.WithFields(logrus.Fields{
@@ -181,7 +170,7 @@ func (xl XL) ReadFile(volume, path string, offset int64) (io.ReadCloser, error)
 			}
 
 			// Join the decoded blocks.
-			err = xl.ReedSolomon.Join(pipeWriter, enBlocks, curBlockSize)
+			err = xl.ReedSolomon.Join(pipeWriter, enBlocks, int(curBlockSize))
 			if err != nil {
 				log.WithFields(logrus.Fields{
 					"volume": volume,
@@ -192,7 +181,7 @@ func (xl XL) ReadFile(volume, path string, offset int64) (io.ReadCloser, error)
 			}
 
 			// Save what's left after reading erasureBlockSize.
-			totalLeft = totalLeft - erasureBlockSize
+			totalLeft = totalLeft - metadata.Erasure.BlockSize
 		}
 
 		// Cleanly end the pipe after a successful decoding.

xl-v1-utils.go

@@ -30,7 +30,7 @@ func checkBlockSize(blocks [][]byte) int {
 
 // calculate the blockSize based on input length and total number of
 // data blocks.
-func getEncodedBlockLen(inputLen, dataBlocks int) (curBlockSize int) {
-	curBlockSize = (inputLen + dataBlocks - 1) / dataBlocks
-	return
+func getEncodedBlockLen(inputLen int64, dataBlocks int) (curBlockSize int64) {
+	curBlockSize = (inputLen + int64(dataBlocks) - 1) / int64(dataBlocks)
+	return curBlockSize
 }

xl-v1.go

@@ -30,7 +30,7 @@ import (
 
 const (
 	// Part metadata file.
-	metadataFile = "part.json"
+	xlMetaV1File = "xl.json"
 	// Maximum erasure blocks.
 	maxErasureBlocks = 16
 )
@@ -325,32 +325,32 @@ func isLeafDirectory(disk StorageAPI, volume, leafPath string) (isLeaf bool) {
 	return true
 }
 
-// extractMetadata - extract file metadata.
-func extractMetadata(disk StorageAPI, volume, path string) (fileMetadata, error) {
-	metadataFilePath := slashpath.Join(path, metadataFile)
+// extractMetadata - extract xl metadata.
+func extractMetadata(disk StorageAPI, volume, path string) (xlMetaV1, error) {
+	xlMetaV1FilePath := slashpath.Join(path, xlMetaV1File)
 	// We are not going to read partial data from metadata file,
 	// read the whole file always.
 	offset := int64(0)
-	metadataReader, err := disk.ReadFile(volume, metadataFilePath, offset)
+	metadataReader, err := disk.ReadFile(volume, xlMetaV1FilePath, offset)
 	if err != nil {
 		log.WithFields(logrus.Fields{
 			"volume": volume,
-			"path":   metadataFilePath,
+			"path":   xlMetaV1FilePath,
 			"offset": offset,
 		}).Errorf("ReadFile failed with %s", err)
-		return nil, err
+		return xlMetaV1{}, err
 	}
 	// Close metadata reader.
 	defer metadataReader.Close()
 
-	metadata, err := fileMetadataDecode(metadataReader)
+	metadata, err := xlMetaV1Decode(metadataReader)
 	if err != nil {
 		log.WithFields(logrus.Fields{
 			"volume": volume,
-			"path":   metadataFilePath,
+			"path":   xlMetaV1FilePath,
 			"offset": offset,
-		}).Errorf("fileMetadataDecode failed with %s", err)
-		return nil, err
+		}).Errorf("xlMetaV1Decode failed with %s", err)
+		return xlMetaV1{}, err
 	}
 	return metadata, nil
 }
@@ -369,25 +369,9 @@ func extractFileInfo(disk StorageAPI, volume, path string) (FileInfo, error) {
 		}).Errorf("extractMetadata failed with %s", err)
 		return FileInfo{}, err
 	}
-	fileSize, err := metadata.GetSize()
-	if err != nil {
-		log.WithFields(logrus.Fields{
-			"volume": volume,
-			"path":   path,
-		}).Errorf("GetSize failed with %s", err)
-		return FileInfo{}, err
-	}
-	fileModTime, err := metadata.GetModTime()
-	if err != nil {
-		log.WithFields(logrus.Fields{
-			"volume": volume,
-			"path":   path,
-		}).Errorf("GetModTime failed with %s", err)
-		return FileInfo{}, err
-	}
-	fileInfo.Size = fileSize
-	fileInfo.Mode = os.FileMode(0644)
-	fileInfo.ModTime = fileModTime
+	fileInfo.Size = metadata.Stat.Size
+	fileInfo.ModTime = metadata.Stat.ModTime
+	fileInfo.Mode = os.FileMode(0644) // This is a file already.
 	return fileInfo, nil
 }
 
@@ -458,7 +442,7 @@ func listFiles(disk StorageAPI, volume, prefix, marker string, recursive bool, c
 		if isLeaf {
 			// For leaf for now we just point to the first block, make it
 			// dynamic in future based on the availability of storage disks.
-			markerPath = slashpath.Join(marker, metadataFile)
+			markerPath = slashpath.Join(marker, xlMetaV1File)
 		}
 	}
 
@@ -478,7 +462,7 @@ func listFiles(disk StorageAPI, volume, prefix, marker string, recursive bool, c
 		}
 		for _, fsFileInfo := range fsFilesInfo {
 			// Skip metadata files.
-			if strings.HasSuffix(fsFileInfo.Name, metadataFile) {
+			if strings.HasSuffix(fsFileInfo.Name, xlMetaV1File) {
 				continue
 			}
 			var fileInfo FileInfo
@@ -518,9 +502,8 @@ func listFiles(disk StorageAPI, volume, prefix, marker string, recursive bool, c
 			// markerPath for the next disk.ListFiles() iteration.
 			markerPath = fsFilesInfo[len(fsFilesInfo)-1].Name
 		}
-		if count == 0 && recursive && !strings.HasSuffix(markerPath, metadataFile) {
-			// If last entry is not part.json then loop once more to check if we
-			// have reached eof.
+		if count == 0 && recursive && !strings.HasSuffix(markerPath, xlMetaV1File) {
+			// If last entry is not xl.json then loop once more to check if we have reached eof.
 			fsFilesInfo, eof, err = disk.ListFiles(volume, prefix, markerPath, recursive, 1)
 			if err != nil {
 				log.WithFields(logrus.Fields{
@@ -533,17 +516,17 @@ func listFiles(disk StorageAPI, volume, prefix, marker string, recursive bool, c
 				return nil, true, err
 			}
 			if !eof {
-				// part.N and part.json are always in pairs and hence this
-				// entry has to be part.json. If not better to manually investigate
+				// file.N and xl.json are always in pairs and hence this
+				// entry has to be xl.json. If not better to manually investigate
 				// and fix it.
 				// For the next ListFiles() call we can safely assume that the
-				// marker is "object/part.json"
-				if !strings.HasSuffix(fsFilesInfo[0].Name, metadataFile) {
+				// marker is "object/xl.json"
+				if !strings.HasSuffix(fsFilesInfo[0].Name, xlMetaV1File) {
 					log.WithFields(logrus.Fields{
 						"volume":          volume,
 						"prefix":          prefix,
 						"fsFileInfo.Name": fsFilesInfo[0].Name,
-					}).Errorf("ListFiles failed with %s, expected %s to be a part.json file.", err, fsFilesInfo[0].Name)
+					}).Errorf("ListFiles failed with %s, expected %s to be a xl.json file.", err, fsFilesInfo[0].Name)
 					return nil, true, errUnexpected
 				}
 			}
@@ -594,30 +577,12 @@ func (xl XL) StatFile(volume, path string) (FileInfo, error) {
 		}()
 	}
 
-	// Extract metadata.
-	size, err := metadata.GetSize()
-	if err != nil {
-		log.WithFields(logrus.Fields{
-			"volume": volume,
-			"path":   path,
-		}).Errorf("GetSize failed with %s", err)
-		return FileInfo{}, err
-	}
-	modTime, err := metadata.GetModTime()
-	if err != nil {
-		log.WithFields(logrus.Fields{
-			"volume": volume,
-			"path":   path,
-		}).Errorf("GetModTime failed with %s", err)
-		return FileInfo{}, err
-	}
-
 	// Return file info.
 	return FileInfo{
 		Volume:  volume,
 		Name:    path,
-		Size:    size,
-		ModTime: modTime,
+		Size:    metadata.Stat.Size,
+		ModTime: metadata.Stat.ModTime,
 		Mode:    os.FileMode(0644),
 	}, nil
 }
@@ -632,7 +597,7 @@ func (xl XL) DeleteFile(volume, path string) error {
 	}
 	// Loop through and delete each chunks.
 	for index, disk := range xl.storageDisks {
-		erasureFilePart := slashpath.Join(path, fmt.Sprintf("part.%d", index))
+		erasureFilePart := slashpath.Join(path, fmt.Sprintf("file.%d", index))
 		err := disk.DeleteFile(volume, erasureFilePart)
 		if err != nil {
 			log.WithFields(logrus.Fields{
@@ -641,8 +606,8 @@ func (xl XL) DeleteFile(volume, path string) error {
 			}).Errorf("DeleteFile failed with %s", err)
 			return err
 		}
-		metadataFilePath := slashpath.Join(path, metadataFile)
-		err = disk.DeleteFile(volume, metadataFilePath)
+		xlMetaV1FilePath := slashpath.Join(path, xlMetaV1File)
+		err = disk.DeleteFile(volume, xlMetaV1FilePath)
 		if err != nil {
 			log.WithFields(logrus.Fields{
 				"volume": volume,