wg.Add(2)
	go func() {
		defer wg.Done()
		srcSize, err := io.Copy(srcSha256, sobj)
		if err != nil {
			fmt.Printf("unreadable on source: %s (%s)\n", srcCtnt.Key, err)
			sourceFailed = true
		} else if srcSize != srcCtnt.Size {
			fmt.Printf("unreadable on source - size differs upon read: %s\n", srcCtnt.Key)
			sourceFailed = true
		}
	}()
	go func() {
		defer wg.Done()
		tgtSize, err := io.Copy(tgtSha256, tobj)

	// Newer versions cannot be read by older software.
	// This will prevent downgrades to incompatible versions.
	xlVersionMajor = 1

	// Non breaking changes.
	// Bumping this is informational, but should be done
	// if any change is made to the data stored, bumping this
	// will allow to detect the exact version later.
	xlVersionMinor = 1
)

func init() {