// Storage class is special, it can be replaced regardless of the
	// metadata directive, if set should be preserved and replaced
	// to the destination metadata.
	sc := r.Header.Get(xhttp.AmzStorageClass)
	if sc == "" {
		sc = r.Form.Get(xhttp.AmzStorageClass)
	}

	// if x-amz-metadata-directive says REPLACE then
	// we extract metadata from the input headers.