TOKYO, Oct 2 (Reuters) - Japanese stocks rose early on Friday as trading resumed after an unprecedented one-day outage on the Tokyo Stock Exchange the previous day due to systems trouble. The Nikkei average and the Topix index were both up around 0.8% at 0006 GMT. The glitch was the result of hardware problem at the exchange’s “Arrowhead” trading system, and a subsequent failure to switch to a back-up, the bourse said on Thursday.