erasure: simplify XL backend operations (#4649) (#4758)

This change provides new implementations of the XL backend operations:
 - create file
 - read   file
 - heal   file
Further this change adds table based tests for all three operations.

This affects also the bitrot algorithm integration. Algorithms are now
integrated in an idiomatic way (like crypto.Hash).
Fixes #4696
Fixes #4649
Fixes #4359

cmd/erasure-readfile_test.go

@@ -18,358 +18,148 @@ package cmd
 
 import (
 	"bytes"
+	crand "crypto/rand"
+	"io"
 	"math/rand"
 	"testing"
 
-	"reflect"
-
 	humanize "github.com/dustin/go-humanize"
 	"github.com/minio/minio/pkg/bpool"
 )
 
-// Tests getReadDisks which returns readable disks slice from which we can
-// read parallelly.
-func testGetReadDisks(t *testing.T, xl *xlObjects) {
-	d := xl.storageDisks
-	testCases := []struct {
-		index     int          // index argument for getReadDisks
-		argDisks  []StorageAPI // disks argument for getReadDisks
-		retDisks  []StorageAPI // disks return value from getReadDisks
-		nextIndex int          // return value from getReadDisks
-		err       error        // error return value from getReadDisks
-	}{
-		// Test case - 1.
-		// When all disks are available, should return data disks.
-		{
-			0,
-			[]StorageAPI{d[0], d[1], d[2], d[3], d[4], d[5], d[6], d[7], d[8], d[9], d[10], d[11], d[12], d[13], d[14], d[15]},
-			[]StorageAPI{d[0], d[1], d[2], d[3], d[4], d[5], d[6], d[7], nil, nil, nil, nil, nil, nil, nil, nil},
-			8,
-			nil,
-		},
-		// Test case - 2.
-		// If a parity disk is down, should return all data disks.
-		{
-			0,
-			[]StorageAPI{d[0], d[1], d[2], d[3], d[4], d[5], d[6], d[7], d[8], nil, d[10], d[11], d[12], d[13], d[14], d[15]},
-			[]StorageAPI{d[0], d[1], d[2], d[3], d[4], d[5], d[6], d[7], nil, nil, nil, nil, nil, nil, nil, nil},
-			8,
-			nil,
-		},
-		// Test case - 3.
-		// If a data disk is down, should return 7 data and 1 parity.
-		{
-			0,
-			[]StorageAPI{nil, d[1], d[2], d[3], d[4], d[5], d[6], d[7], d[8], d[9], d[10], d[11], d[12], d[13], d[14], d[15]},
-			[]StorageAPI{nil, d[1], d[2], d[3], d[4], d[5], d[6], d[7], d[8], nil, nil, nil, nil, nil, nil, nil},
-			9,
-			nil,
-		},
-		// Test case - 4.
-		// If 7 data disks are down, should return 1 data and 7 parity.
-		{
-			0,
-			[]StorageAPI{nil, nil, nil, nil, nil, nil, nil, d[7], d[8], d[9], d[10], d[11], d[12], d[13], d[14], d[15]},
-			[]StorageAPI{nil, nil, nil, nil, nil, nil, nil, d[7], d[8], d[9], d[10], d[11], d[12], d[13], d[14], nil},
-			15,
-			nil,
-		},
-		// Test case - 5.
-		// When 2 disks fail during parallelRead, next call to getReadDisks should return 3 disks
-		{
-			8,
-			[]StorageAPI{nil, nil, d[2], d[3], d[4], d[5], d[6], d[7], d[8], d[9], d[10], d[11], d[12], d[13], d[14], d[15]},
-			[]StorageAPI{nil, nil, nil, nil, nil, nil, nil, nil, d[8], d[9], nil, nil, nil, nil, nil, nil},
-			10,
-			nil,
-		},
-		// Test case - 6.
-		// If 2 disks again fail from the 3 disks returned previously, return next 2 disks
-		{
-			11,
-			[]StorageAPI{nil, nil, d[2], d[3], d[4], d[5], d[6], d[7], nil, nil, d[10], d[11], d[12], d[13], d[14], d[15]},
-			[]StorageAPI{nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, d[11], nil, nil, nil, nil},
-			12,
-			nil,
-		},
-		// Test case - 7.
-		// No more disks are available for read, return error
-		{
-			13,
-			[]StorageAPI{nil, nil, d[2], d[3], d[4], d[5], d[6], d[7], nil, nil, d[10], nil, nil, nil, nil, nil},
-			nil,
-			0,
-			errXLReadQuorum,
-		},
-	}
-
-	for i, test := range testCases {
-		disks, nextIndex, err := getReadDisks(test.argDisks, test.index, xl.dataBlocks)
-		if errorCause(err) != test.err {
-			t.Errorf("test-case %d - expected error : %s, got : %s", i+1, test.err, err)
-			continue
-		}
-		if test.nextIndex != nextIndex {
-			t.Errorf("test-case %d - expected nextIndex: %d, got : %d", i+1, test.nextIndex, nextIndex)
-			continue
-		}
-		if !reflect.DeepEqual(test.retDisks, disks) {
-			t.Errorf("test-case %d : incorrect disks returned. expected %+v, got %+v", i+1, test.retDisks, disks)
-			continue
-		}
-	}
-}
-
-// Test for isSuccessDataBlocks and isSuccessDecodeBlocks.
-func TestIsSuccessBlocks(t *testing.T) {
-	dataBlocks := 8
-	testCases := []struct {
-		enBlocks      [][]byte // data and parity blocks.
-		successData   bool     // expected return value of isSuccessDataBlocks()
-		successDecode bool     // expected return value of isSuccessDecodeBlocks()
-	}{
-		{
-			// When all data and partity blocks are available.
-			[][]byte{
-				{'a'}, {'a'}, {'a'}, {'a'}, {'a'}, {'a'}, {'a'}, {'a'},
-				{'a'}, {'a'}, {'a'}, {'a'}, {'a'}, {'a'}, {'a'}, {'a'},
-			},
-			true,
-			true,
-		},
-		{
-			// When one data block is not available.
-			[][]byte{
-				nil, {'a'}, {'a'}, {'a'}, {'a'}, {'a'}, {'a'}, {'a'},
-				{'a'}, {'a'}, {'a'}, {'a'}, {'a'}, {'a'}, {'a'}, {'a'},
-			},
-			false,
-			true,
-		},
-		{
-			// When one data and all parity are available, enough for reedsolomon.Reconstruct()
-			[][]byte{
-				nil, nil, nil, nil, nil, nil, nil, {'a'},
-				{'a'}, {'a'}, {'a'}, {'a'}, {'a'}, {'a'}, {'a'}, {'a'},
-			},
-			false,
-			true,
-		},
-		{
-			// When all data disks are not available, enough for reedsolomon.Reconstruct()
-			[][]byte{
-				nil, nil, nil, nil, nil, nil, nil, nil,
-				{'a'}, {'a'}, {'a'}, {'a'}, {'a'}, {'a'}, {'a'}, {'a'},
-			},
-			false,
-			true,
-		},
-		{
-			// Not enough disks for reedsolomon.Reconstruct()
-			[][]byte{
-				nil, nil, nil, nil, nil, nil, nil, nil,
-				nil, {'a'}, {'a'}, {'a'}, {'a'}, {'a'}, {'a'}, {'a'},
-			},
-			false,
-			false,
-		},
-	}
-
-	for i, test := range testCases {
-		got := isSuccessDataBlocks(test.enBlocks, dataBlocks)
-		if test.successData != got {
-			t.Errorf("test-case %d : expected %v got %v", i+1, test.successData, got)
-		}
-		got = isSuccessDecodeBlocks(test.enBlocks, dataBlocks)
-		if test.successDecode != got {
-			t.Errorf("test-case %d : expected %v got %v", i+1, test.successDecode, got)
-		}
-	}
-}
-
-// Wrapper function for testGetReadDisks, testShuffleDisks.
-func TestErasureReadUtils(t *testing.T) {
-	nDisks := 16
-	disks, err := getRandomDisks(nDisks)
-	if err != nil {
-		t.Fatal(err)
-	}
-	objLayer, _, err := initObjectLayer(mustGetNewEndpointList(disks...))
-	if err != nil {
-		removeRoots(disks)
-		t.Fatal(err)
-	}
-	defer removeRoots(disks)
-	xl := objLayer.(*xlObjects)
-	testGetReadDisks(t, xl)
-}
-
-// Simulates a faulty disk for ReadFile()
-type ReadDiskDown struct {
-	*posix
-}
-
-func (r ReadDiskDown) ReadFile(volume string, path string, offset int64, buf []byte) (n int64, err error) {
+func (d badDisk) ReadFile(volume string, path string, offset int64, buf []byte) (n int64, err error) {
 	return 0, errFaultyDisk
 }
 
-func (r ReadDiskDown) ReadFileWithVerify(volume string, path string, offset int64, buf []byte,
-	algo HashAlgo, expectedHash string) (n int64, err error) {
-
+func (d badDisk) ReadFileWithVerify(volume string, path string, offset int64, buf []byte, verifier *BitrotVerifier) (n int64, err error) {
 	return 0, errFaultyDisk
 }
 
-func TestErasureReadFileDiskFail(t *testing.T) {
-	// Initialize environment needed for the test.
-	dataBlocks := 7
-	parityBlocks := 7
-	blockSize := int64(blockSizeV1)
-	setup, err := newErasureTestSetup(dataBlocks, parityBlocks, blockSize)
-	if err != nil {
-		t.Error(err)
-		return
-	}
-	defer setup.Remove()
-
-	disks := setup.disks
-
-	// Prepare a slice of 1humanize.MiByte with random data.
-	data := make([]byte, 1*humanize.MiByte)
-	length := int64(len(data))
-	_, err = rand.Read(data)
-	if err != nil {
-		t.Fatal(err)
-	}
-
-	// Create a test file to read from.
-	_, size, checkSums, err := erasureCreateFile(disks, "testbucket", "testobject", bytes.NewReader(data), true, blockSize, dataBlocks, parityBlocks, bitRotAlgo, dataBlocks+1)
-	if err != nil {
-		t.Fatal(err)
-	}
-	if size != length {
-		t.Errorf("erasureCreateFile returned %d, expected %d", size, length)
-	}
-
-	// create byte pool which will be used by erasureReadFile for
-	// reading from disks and erasure decoding.
-	chunkSize := getChunkSize(blockSize, dataBlocks)
-	pool := bpool.NewBytePool(chunkSize, len(disks))
-
-	buf := &bytes.Buffer{}
-	_, err = erasureReadFile(buf, disks, "testbucket", "testobject", 0, length, length, blockSize, dataBlocks, parityBlocks, checkSums, bitRotAlgo, pool)
-	if err != nil {
-		t.Error(err)
-	}
-	if !bytes.Equal(buf.Bytes(), data) {
-		t.Error("Contents of the erasure coded file differs")
-	}
-
-	// 2 disks down. Read should succeed.
-	disks[4] = ReadDiskDown{disks[4].(*posix)}
-	disks[5] = ReadDiskDown{disks[5].(*posix)}
-
-	buf.Reset()
-	_, err = erasureReadFile(buf, disks, "testbucket", "testobject", 0, length, length, blockSize, dataBlocks, parityBlocks, checkSums, bitRotAlgo, pool)
-	if err != nil {
-		t.Error(err)
-	}
-	if !bytes.Equal(buf.Bytes(), data) {
-		t.Error("Contents of the erasure coded file differs")
-	}
-
-	// 4 more disks down. 6 disks down in total. Read should succeed.
-	disks[6] = ReadDiskDown{disks[6].(*posix)}
-	disks[8] = ReadDiskDown{disks[8].(*posix)}
-	disks[9] = ReadDiskDown{disks[9].(*posix)}
-	disks[11] = ReadDiskDown{disks[11].(*posix)}
-
-	buf.Reset()
-	_, err = erasureReadFile(buf, disks, "testbucket", "testobject", 0, length, length, blockSize, dataBlocks, parityBlocks, checkSums, bitRotAlgo, pool)
-	if err != nil {
-		t.Error(err)
-	}
-	if !bytes.Equal(buf.Bytes(), data) {
-		t.Error("Contents of the erasure coded file differs")
-	}
-
-	// 2 more disk down. 8 disks down in total. Read should fail.
-	disks[12] = ReadDiskDown{disks[12].(*posix)}
-	disks[13] = ReadDiskDown{disks[13].(*posix)}
-	buf.Reset()
-	_, err = erasureReadFile(buf, disks, "testbucket", "testobject", 0, length, length, blockSize, dataBlocks, parityBlocks, checkSums, bitRotAlgo, pool)
-	if errorCause(err) != errXLReadQuorum {
-		t.Fatal("expected errXLReadQuorum error")
-	}
+var erasureReadFileTests = []struct {
+	dataBlocks                   int
+	onDisks, offDisks            int
+	blocksize, data              int64
+	offset                       int64
+	length                       int64
+	algorithm                    BitrotAlgorithm
+	shouldFail, shouldFailQuorum bool
+}{
+	{dataBlocks: 2, onDisks: 4, offDisks: 0, blocksize: int64(blockSizeV1), data: oneMiByte, offset: 0, length: oneMiByte, algorithm: BLAKE2b512, shouldFail: false, shouldFailQuorum: false},                                                         // 0
+	{dataBlocks: 3, onDisks: 6, offDisks: 0, blocksize: int64(blockSizeV1), data: oneMiByte, offset: 0, length: oneMiByte, algorithm: SHA256, shouldFail: false, shouldFailQuorum: false},                                                             // 1
+	{dataBlocks: 4, onDisks: 8, offDisks: 0, blocksize: int64(blockSizeV1), data: oneMiByte, offset: 0, length: oneMiByte, algorithm: DefaultBitrotAlgorithm, shouldFail: false, shouldFailQuorum: false},                                             // 2
+	{dataBlocks: 5, onDisks: 10, offDisks: 0, blocksize: int64(blockSizeV1), data: oneMiByte, offset: 1, length: oneMiByte - 1, algorithm: BLAKE2b512, shouldFail: false, shouldFailQuorum: false},                                                    // 3
+	{dataBlocks: 6, onDisks: 12, offDisks: 0, blocksize: int64(oneMiByte), data: oneMiByte, offset: oneMiByte, length: 0, algorithm: BLAKE2b512, shouldFail: false, shouldFailQuorum: false},                                                          // 4
+	{dataBlocks: 7, onDisks: 14, offDisks: 0, blocksize: int64(oneMiByte), data: oneMiByte, offset: 3, length: 1024, algorithm: DefaultBitrotAlgorithm, shouldFail: false, shouldFailQuorum: false},                                                   // 5
+	{dataBlocks: 8, onDisks: 16, offDisks: 0, blocksize: int64(oneMiByte), data: oneMiByte, offset: 4, length: 8 * 1024, algorithm: DefaultBitrotAlgorithm, shouldFail: false, shouldFailQuorum: false},                                               // 6
+	{dataBlocks: 7, onDisks: 14, offDisks: 7, blocksize: int64(blockSizeV1), data: oneMiByte, offset: oneMiByte, length: 1, algorithm: DefaultBitrotAlgorithm, shouldFail: true, shouldFailQuorum: false},                                             // 7
+	{dataBlocks: 6, onDisks: 12, offDisks: 6, blocksize: int64(blockSizeV1), data: oneMiByte, offset: 0, length: oneMiByte, algorithm: DefaultBitrotAlgorithm, shouldFail: false, shouldFailQuorum: false},                                            // 8
+	{dataBlocks: 5, onDisks: 10, offDisks: 5, blocksize: int64(oneMiByte), data: oneMiByte, offset: 0, length: oneMiByte, algorithm: BLAKE2b512, shouldFail: false, shouldFailQuorum: false},                                                          // 9
+	{dataBlocks: 4, onDisks: 8, offDisks: 4, blocksize: int64(blockSizeV1), data: oneMiByte, offset: 0, length: oneMiByte, algorithm: SHA256, shouldFail: false, shouldFailQuorum: false},                                                             // 10
+	{dataBlocks: 3, onDisks: 6, offDisks: 3, blocksize: int64(oneMiByte), data: oneMiByte, offset: 0, length: oneMiByte, algorithm: DefaultBitrotAlgorithm, shouldFail: false, shouldFailQuorum: false},                                               // 11
+	{dataBlocks: 2, onDisks: 4, offDisks: 2, blocksize: int64(blockSizeV1), data: oneMiByte, offset: 0, length: oneMiByte, algorithm: DefaultBitrotAlgorithm, shouldFail: false, shouldFailQuorum: false},                                             // 12
+	{dataBlocks: 2, onDisks: 4, offDisks: 1, blocksize: int64(oneMiByte), data: oneMiByte, offset: 0, length: oneMiByte, algorithm: DefaultBitrotAlgorithm, shouldFail: false, shouldFailQuorum: false},                                               // 13
+	{dataBlocks: 3, onDisks: 6, offDisks: 2, blocksize: int64(oneMiByte), data: oneMiByte, offset: 0, length: oneMiByte, algorithm: DefaultBitrotAlgorithm, shouldFail: false, shouldFailQuorum: false},                                               // 14
+	{dataBlocks: 4, onDisks: 8, offDisks: 3, blocksize: int64(2 * oneMiByte), data: oneMiByte, offset: 0, length: oneMiByte, algorithm: DefaultBitrotAlgorithm, shouldFail: false, shouldFailQuorum: false},                                           // 15
+	{dataBlocks: 5, onDisks: 10, offDisks: 6, blocksize: int64(oneMiByte), data: oneMiByte, offset: 0, length: oneMiByte, algorithm: DefaultBitrotAlgorithm, shouldFail: false, shouldFailQuorum: true},                                               // 16
+	{dataBlocks: 5, onDisks: 10, offDisks: 2, blocksize: int64(blockSizeV1), data: 2 * oneMiByte, offset: oneMiByte, length: oneMiByte, algorithm: DefaultBitrotAlgorithm, shouldFail: false, shouldFailQuorum: false},                                // 17
+	{dataBlocks: 5, onDisks: 10, offDisks: 1, blocksize: int64(blockSizeV1), data: oneMiByte, offset: 0, length: oneMiByte, algorithm: BLAKE2b512, shouldFail: false, shouldFailQuorum: false},                                                        // 18
+	{dataBlocks: 6, onDisks: 12, offDisks: 3, blocksize: int64(blockSizeV1), data: oneMiByte, offset: 0, length: oneMiByte, algorithm: SHA256, shouldFail: false, shouldFailQuorum: false},                                                            // 19
+	{dataBlocks: 6, onDisks: 12, offDisks: 7, blocksize: int64(blockSizeV1), data: oneMiByte, offset: 0, length: oneMiByte, algorithm: DefaultBitrotAlgorithm, shouldFail: false, shouldFailQuorum: true},                                             // 20
+	{dataBlocks: 8, onDisks: 16, offDisks: 8, blocksize: int64(blockSizeV1), data: oneMiByte, offset: 0, length: oneMiByte, algorithm: DefaultBitrotAlgorithm, shouldFail: false, shouldFailQuorum: false},                                            // 21
+	{dataBlocks: 8, onDisks: 16, offDisks: 9, blocksize: int64(oneMiByte), data: oneMiByte, offset: 0, length: oneMiByte, algorithm: DefaultBitrotAlgorithm, shouldFail: false, shouldFailQuorum: true},                                               // 22
+	{dataBlocks: 8, onDisks: 16, offDisks: 7, blocksize: int64(blockSizeV1), data: oneMiByte, offset: 0, length: oneMiByte, algorithm: DefaultBitrotAlgorithm, shouldFail: false, shouldFailQuorum: false},                                            // 23
+	{dataBlocks: 2, onDisks: 4, offDisks: 1, blocksize: int64(blockSizeV1), data: oneMiByte, offset: 0, length: oneMiByte, algorithm: DefaultBitrotAlgorithm, shouldFail: false, shouldFailQuorum: false},                                             // 24
+	{dataBlocks: 2, onDisks: 4, offDisks: 0, blocksize: int64(blockSizeV1), data: oneMiByte, offset: 0, length: oneMiByte, algorithm: DefaultBitrotAlgorithm, shouldFail: false, shouldFailQuorum: false},                                             // 25
+	{dataBlocks: 2, onDisks: 4, offDisks: 0, blocksize: int64(blockSizeV1), data: oneMiByte, offset: 0, length: oneMiByte, algorithm: 0, shouldFail: true, shouldFailQuorum: false},                                                                   // 26
+	{dataBlocks: 2, onDisks: 4, offDisks: 0, blocksize: int64(blockSizeV1), data: int64(blockSizeV1) + 1, offset: 0, length: int64(blockSizeV1) + 1, algorithm: BLAKE2b512, shouldFail: false, shouldFailQuorum: false},                               // 27
+	{dataBlocks: 2, onDisks: 4, offDisks: 0, blocksize: int64(blockSizeV1), data: int64(2 * blockSizeV1), offset: 12, length: int64(blockSizeV1) + 17, algorithm: BLAKE2b512, shouldFail: false, shouldFailQuorum: false},                             // 28
+	{dataBlocks: 3, onDisks: 6, offDisks: 0, blocksize: int64(blockSizeV1), data: int64(2 * blockSizeV1), offset: 1023, length: int64(blockSizeV1) + 1024, algorithm: DefaultBitrotAlgorithm, shouldFail: false, shouldFailQuorum: false},             // 29
+	{dataBlocks: 4, onDisks: 8, offDisks: 0, blocksize: int64(blockSizeV1), data: int64(2 * blockSizeV1), offset: 11, length: int64(blockSizeV1) + 2*1024, algorithm: DefaultBitrotAlgorithm, shouldFail: false, shouldFailQuorum: false},             // 30
+	{dataBlocks: 6, onDisks: 12, offDisks: 0, blocksize: int64(blockSizeV1), data: int64(2 * blockSizeV1), offset: 512, length: int64(blockSizeV1) + 8*1024, algorithm: DefaultBitrotAlgorithm, shouldFail: false, shouldFailQuorum: false},           // 31
+	{dataBlocks: 8, onDisks: 16, offDisks: 0, blocksize: int64(blockSizeV1), data: int64(2 * blockSizeV1), offset: int64(blockSizeV1), length: int64(blockSizeV1) - 1, algorithm: DefaultBitrotAlgorithm, shouldFail: false, shouldFailQuorum: false}, // 32
+	{dataBlocks: 2, onDisks: 4, offDisks: 0, blocksize: int64(blockSizeV1), data: int64(oneMiByte), offset: -1, length: 3, algorithm: DefaultBitrotAlgorithm, shouldFail: true, shouldFailQuorum: false},                                              // 33
+	{dataBlocks: 2, onDisks: 4, offDisks: 0, blocksize: int64(blockSizeV1), data: int64(oneMiByte), offset: 1024, length: -1, algorithm: DefaultBitrotAlgorithm, shouldFail: true, shouldFailQuorum: false},                                           // 34
+	{dataBlocks: 4, onDisks: 6, offDisks: 0, blocksize: int64(blockSizeV1), data: int64(blockSizeV1), offset: 0, length: int64(blockSizeV1), algorithm: BLAKE2b512, shouldFail: false, shouldFailQuorum: false},                                       // 35
+	{dataBlocks: 4, onDisks: 6, offDisks: 1, blocksize: int64(blockSizeV1), data: int64(2 * blockSizeV1), offset: 12, length: int64(blockSizeV1) + 17, algorithm: BLAKE2b512, shouldFail: false, shouldFailQuorum: false},                             // 36
+	{dataBlocks: 4, onDisks: 6, offDisks: 3, blocksize: int64(blockSizeV1), data: int64(2 * blockSizeV1), offset: 1023, length: int64(blockSizeV1) + 1024, algorithm: DefaultBitrotAlgorithm, shouldFail: false, shouldFailQuorum: true},              // 37
+	{dataBlocks: 8, onDisks: 12, offDisks: 4, blocksize: int64(blockSizeV1), data: int64(2 * blockSizeV1), offset: 11, length: int64(blockSizeV1) + 2*1024, algorithm: DefaultBitrotAlgorithm, shouldFail: false, shouldFailQuorum: false},            // 38
 }
 
-func TestErasureReadFileOffsetLength(t *testing.T) {
-	// Initialize environment needed for the test.
-	dataBlocks := 7
-	parityBlocks := 7
-	blockSize := int64(1 * humanize.MiByte)
-	setup, err := newErasureTestSetup(dataBlocks, parityBlocks, blockSize)
-	if err != nil {
-		t.Error(err)
-		return
-	}
-	defer setup.Remove()
-
-	disks := setup.disks
-
-	// Prepare a slice of 5humanize.MiByte with random data.
-	data := make([]byte, 5*humanize.MiByte)
-	length := int64(len(data))
-	_, err = rand.Read(data)
-	if err != nil {
-		t.Fatal(err)
-	}
-
-	// Create a test file to read from.
-	_, size, checkSums, err := erasureCreateFile(disks, "testbucket", "testobject", bytes.NewReader(data), true, blockSize, dataBlocks, parityBlocks, bitRotAlgo, dataBlocks+1)
-	if err != nil {
-		t.Fatal(err)
-	}
-	if size != length {
-		t.Errorf("erasureCreateFile returned %d, expected %d", size, length)
-	}
-
-	testCases := []struct {
-		offset, length int64
-	}{
-		// Full file.
-		{0, length},
-		// Read nothing.
-		{length, 0},
-		// 2nd block.
-		{blockSize, blockSize},
-		// Test cases for random offsets and lengths.
-		{blockSize - 1, 2},
-		{blockSize - 1, blockSize + 1},
-		{blockSize + 1, blockSize - 1},
-		{blockSize + 1, blockSize},
-		{blockSize + 1, blockSize + 1},
-		{blockSize*2 - 1, blockSize + 1},
-		{length - 1, 1},
-		{length - blockSize, blockSize},
-		{length - blockSize - 1, blockSize},
-		{length - blockSize - 1, blockSize + 1},
-	}
-	chunkSize := getChunkSize(blockSize, dataBlocks)
-	pool := bpool.NewBytePool(chunkSize, len(disks))
-
-	// Compare the data read from file with "data" byte array.
-	for i, testCase := range testCases {
-		expected := data[testCase.offset:(testCase.offset + testCase.length)]
-		buf := &bytes.Buffer{}
-		_, err = erasureReadFile(buf, disks, "testbucket", "testobject", testCase.offset, testCase.length, length, blockSize, dataBlocks, parityBlocks, checkSums, bitRotAlgo, pool)
+func TestErasureReadFile(t *testing.T) {
+	for i, test := range erasureReadFileTests {
+		setup, err := newErasureTestSetup(test.dataBlocks, test.onDisks-test.dataBlocks, test.blocksize)
 		if err != nil {
-			t.Error(err)
-			continue
+			t.Fatalf("Test %d: failed to create test setup: %v", i, err)
 		}
-		got := buf.Bytes()
-		if !bytes.Equal(expected, got) {
-			t.Errorf("Test %d : read data is different from what was expected", i+1)
+		storage, err := NewErasureStorage(setup.disks, test.dataBlocks, test.onDisks-test.dataBlocks)
+		if err != nil {
+			setup.Remove()
+			t.Fatalf("Test %d: failed to create ErasureStorage: %v", i, err)
 		}
+
+		data := make([]byte, test.data)
+		if _, err = io.ReadFull(crand.Reader, data); err != nil {
+			setup.Remove()
+			t.Fatalf("Test %d: failed to generate random test data: %v", i, err)
+		}
+		writeAlgorithm := test.algorithm
+		if !test.algorithm.Available() {
+			writeAlgorithm = DefaultBitrotAlgorithm
+		}
+		buffer := make([]byte, test.blocksize, 2*test.blocksize)
+		file, err := storage.CreateFile(bytes.NewReader(data[:]), "testbucket", "object", buffer, writeAlgorithm, test.dataBlocks+1)
+		if err != nil {
+			setup.Remove()
+			t.Fatalf("Test %d: failed to create erasure test file: %v", i, err)
+		}
+		pool := bpool.NewBytePool(getChunkSize(test.blocksize, test.dataBlocks), len(storage.disks))
+		writer := bytes.NewBuffer(nil)
+		readInfo, err := storage.ReadFile(writer, "testbucket", "object", test.offset, test.length, test.data, file.Checksums, test.algorithm, test.blocksize, pool)
+		if err != nil && !test.shouldFail {
+			t.Errorf("Test %d: should pass but failed with: %v", i, err)
+		}
+		if err == nil && test.shouldFail {
+			t.Errorf("Test %d: should fail but it passed", i)
+		}
+		if err == nil {
+			if readInfo.Size != test.length {
+				t.Errorf("Test %d: read returns wrong number of bytes: got: #%d want: #%d", i, readInfo.Size, test.length)
+			}
+			if readInfo.Algorithm != test.algorithm {
+				t.Errorf("Test %d: read returns wrong algorithm: got: %v want: %v", i, readInfo.Algorithm, test.algorithm)
+			}
+			if content := writer.Bytes(); !bytes.Equal(content, data[test.offset:test.offset+test.length]) {
+				t.Errorf("Test %d: read retruns wrong file content", i)
+			}
+		}
+		if err == nil && !test.shouldFail {
+			writer.Reset()
+			for j := range storage.disks[:test.offDisks] {
+				storage.disks[j] = badDisk{nil}
+			}
+			if test.offDisks > 0 {
+				storage.disks[0] = OfflineDisk
+			}
+			readInfo, err = storage.ReadFile(writer, "testbucket", "object", test.offset, test.length, test.data, file.Checksums, test.algorithm, test.blocksize, pool)
+			if err != nil && !test.shouldFailQuorum {
+				t.Errorf("Test %d: should pass but failed with: %v", i, err)
+			}
+			if err == nil && test.shouldFailQuorum {
+				t.Errorf("Test %d: should fail but it passed", i)
+			}
+			if !test.shouldFailQuorum {
+				if readInfo.Size != test.length {
+					t.Errorf("Test %d: read returns wrong number of bytes: got: #%d want: #%d", i, readInfo.Size, test.length)
+				}
+				if readInfo.Algorithm != test.algorithm {
+					t.Errorf("Test %d: read returns wrong algorithm: got: %v want: %v", i, readInfo.Algorithm, test.algorithm)
+				}
+				if content := writer.Bytes(); !bytes.Equal(content, data[test.offset:test.offset+test.length]) {
+					t.Errorf("Test %d: read retruns wrong file content", i)
+				}
+			}
+		}
+		setup.Remove()
 	}
 }
 
@@ -390,8 +180,10 @@ func TestErasureReadFileRandomOffsetLength(t *testing.T) {
 	}
 	defer setup.Remove()
 
-	disks := setup.disks
-
+	storage, err := NewErasureStorage(setup.disks, dataBlocks, parityBlocks)
+	if err != nil {
+		t.Fatalf("failed to create ErasureStorage: %v", err)
+	}
 	// Prepare a slice of 5MiB with random data.
 	data := make([]byte, 5*humanize.MiByte)
 	length := int64(len(data))
@@ -404,12 +196,13 @@ func TestErasureReadFileRandomOffsetLength(t *testing.T) {
 	iterations := 10000
 
 	// Create a test file to read from.
-	_, size, checkSums, err := erasureCreateFile(disks, "testbucket", "testobject", bytes.NewReader(data), true, blockSize, dataBlocks, parityBlocks, bitRotAlgo, dataBlocks+1)
+	buffer := make([]byte, blockSize, 2*blockSize)
+	file, err := storage.CreateFile(bytes.NewReader(data), "testbucket", "testobject", buffer, DefaultBitrotAlgorithm, dataBlocks+1)
 	if err != nil {
 		t.Fatal(err)
 	}
-	if size != length {
-		t.Errorf("erasureCreateFile returned %d, expected %d", size, length)
+	if file.Size != length {
+		t.Errorf("erasureCreateFile returned %d, expected %d", file.Size, length)
 	}
 
 	// To generate random offset/length.
@@ -418,7 +211,7 @@ func TestErasureReadFileRandomOffsetLength(t *testing.T) {
 	// create pool buffer which will be used by erasureReadFile for
 	// reading from disks and erasure decoding.
 	chunkSize := getChunkSize(blockSize, dataBlocks)
-	pool := bpool.NewBytePool(chunkSize, len(disks))
+	pool := bpool.NewBytePool(chunkSize, len(storage.disks))
 
 	buf := &bytes.Buffer{}
 
@@ -429,7 +222,7 @@ func TestErasureReadFileRandomOffsetLength(t *testing.T) {
 
 		expected := data[offset : offset+readLen]
 
-		_, err = erasureReadFile(buf, disks, "testbucket", "testobject", offset, readLen, length, blockSize, dataBlocks, parityBlocks, checkSums, bitRotAlgo, pool)
+		_, err = storage.ReadFile(buf, "testbucket", "testobject", offset, readLen, length, file.Checksums, DefaultBitrotAlgorithm, blockSize, pool)
 		if err != nil {
 			t.Fatal(err, offset, readLen)
 		}