out.writeShort(DataTransferProtocol.OP_STATUS_SUCCESS); // send op status
long read = blockSender.sendBlock(out, baseStream, null); // send data
boolean isBlockFinalized = datanode.data.isBlockFinalized(namespaceId, block);
long blockLength = datanode.data.getVisibleLength(namespaceId, block);
out.writeBoolean(isBlockFinalized);
out.writeLong(blockLength);
out.flush();
if (blockSender.isBlockReadFully()) {
// See if client verification succeeded.