type ObjectLayer interface {
	// Locking operations on object.
	NewNSLock(bucket string, objects ...string) RWLocker

	// Storage operations.
	Shutdown(context.Context) error
	NSScanner(ctx context.Context, updates chan<- DataUsageInfo, wantCycle uint32, scanMode madmin.HealScanMode) error
	BackendInfo() madmin.BackendInfo
	Legacy() bool // Only returns true for deployments which use CRCMOD as its object distribution algorithm.

	if !dstOpts.NoAuditLog {
		auditObjectErasureSet(ctx, "CopyObject", dstObject, &er)
	}

	// This call shouldn't be used for anything other than metadata updates or adding self referential versions.
	if !srcInfo.metadataOnly {
		return oi, NotImplemented{}
	}

	if !dstOpts.NoLock {
		lk := er.NewNSLock(dstBucket, dstObject)

	metadata := cloneMSS(objInfo.UserDefined)

	// update self with restore metadata
	if rreq.Type != SelectRestoreRequest {
		objInfo.metadataOnly = true // Perform only metadata updates.
		metadata[xhttp.AmzRestoreExpiryDays] = strconv.Itoa(rreq.Days)
		metadata[xhttp.AmzRestoreRequestDate] = time.Now().UTC().Format(http.TimeFormat)
		if alreadyRestored {