Arr is Warriors' highest appearance-maker in the current squad, having played 137 times for his hometown club.
He made his debut against London Irish in 2007 and was named Player-of-the-Year as he helped his side to the RFU Championship title in 2011.
He said: "I'm really pleased to sign a new contract to be part of the club's future. I have enjoyed my time here and have no doubt there are good times in front of us.
"It's not been an easy season but things have progressed rapidly behind the scenes and I am confident this club will be successful."
Fatiaki has made 30 appearances for Warriors since joining the club in 2011 - 17 of which have come under Ryan.
The powerful centre made his international debut in 2009 and is seen as one of the brightest talents in Fijian rugby.
He said: "I am very pleased to have signed a new contract at Warriors. I enjoy playing my rugby at Sixways and believe the club is moving in the right direction. Warriors brought me to England and I feel a strong connection with the club."
Warriors Director of Rugby Dean Ryan said: "It is fantastic to see Jonny and Ravai commit their future to Warriors as we look to take the club to the next level. They are both talented indviduals and I know this news will be welcomed by everyone associated with the club."