Jay O'Donald has been appointed vice president of marketing for Emulex Corp. in Costa Mesa. He will be responsible for domestic and international product marketing and customer service as well as sales support programs. O'Donald, 42, had been Eastern regional sales manager for Emulex from 1980 until he was promoted to director of national accounts in October 1984. He had been publishing systems product manager for six years at Hendrix Electronics in New Hampshire before he joined Emulex. Emulex is a manufacturer of computer products, including disc and tape controllers and packaged subsystems.