Temp buffer turns out even slower
qglBindBuffer( bufferType, tempBuff );
qglBufferData( bufferType, length, mapBuff, bufferUsage );
qglBindBuffer( GL_COPY_READ_BUFFER, tempBuff );
qglBindBuffer( GL_COPY_WRITE_BUFFER, bufferObject );
qglCopyBufferSubData( GL_COPY_READ_BUFFER, GL_COPY_WRITE_BUFFER, 0, lastMapOffset, length );
qglBufferData( bufferType, length, NULL, bufferUsage );