if errs[j] != nil {
					t.Fatalf("expected error to be nil: %s", errs[j])
				}
				partsMetadata[j].ModTime = test.modTimes[j]
			}

			if erasureDisks, err = writeUniqueFileInfo(ctx, erasureDisks, "", bucket, object, partsMetadata, diskCount(erasureDisks)); err != nil {
				t.Fatal(ctx, err)
			}

			tamperedIndex := -1
			switch test._tamperBackend {
			case deletePart:

		for i := 0; i <= f; i++ {
			diskErrors[i] = nil
		}
		erasureDisks := xl.getDisks()
		for i := range erasureDisks[:9] {
			switch diskType := erasureDisks[i].(type) {
			case *naughtyDisk:
				erasureDisks[i] = newNaughtyDisk(diskType.disk, diskErrors, errFaultyDisk)
			default:
				erasureDisks[i] = newNaughtyDisk(erasureDisks[i], diskErrors, errFaultyDisk)
			}
		}
		z.serverPools[0].erasureDisksMu.Lock()

// current design.
type erasureSets struct {
	sets []*erasureObjects

	// Reference format.
	format *formatErasureV3

	// erasureDisks mutex to lock erasureDisks.
	erasureDisksMu sync.RWMutex

	// Re-ordered list of disks per set.
	erasureDisks [][]StorageAPI

	// Distributed locker clients.
	erasureLockers setsDsyncLockers

	// Distributed lock owner (constant per running instance).

	// Now check if we actually wrote to backend (regardless of the response
	// returned by the server).
	z := obj.(*erasureServerPools)
	xl := z.serverPools[0].sets[0]
	erasureDisks := xl.getDisks()
	parts, errs := readAllFileInfo(ctx, erasureDisks, "", bucketName, objectName, "", false, false)
	for i := range parts {
		if errs[i] == nil {
			if parts[i].Name == objectName {

	// Now check if we actually wrote to backend (regardless of the response
	// returned by the server).
	z := obj.(*erasureServerPools)
	xl := z.serverPools[0].sets[0]
	erasureDisks := xl.getDisks()
	parts, errs := readAllFileInfo(ctx, erasureDisks, "", bucketName, objectName+"/upload.txt", "", false, false)
	for i := range parts {
		if errs[i] == nil {
			if parts[i].Name == objectName+"/upload.txt" {