Their first meeting this season in November was played in terrible conditions at Scotstoun and ended 6-0 to Leinster while the match at the RDS was another thriller - the Irish province coming through 22-17 despite the Warriors again scoring two tries to their opponents' one.
Another classic is in store on Saturday with both sides hitting their straps at present - the Warriors have scored the most tries in the RaboDirect PRO12 this season and arrive on the back of wins over the Ospreys and away to Connacht last time out while Leinster have won ten of their last 11 in the league.
They have also been in destructive form in romping to the Amlin Challenge Cup final and Townsend is only too aware of the quality awaiting his side.
"We played there six or seven weeks ago and it was a really good game," said Townsend.
"We had a chance to win at the end but a pass was deemed forward when we probably would have scored.
"They have been the best team in Europe for the last couple of seasons and I think they are back on their best form.
"Leinster have set the benchmark in European rugby for the last three or four seasons and we are under no illusions as to the size of the challenge that awaits us in Dublin.
"Winning in Galway has created vital momentum for us after our home victory against the Ospreys. It was also important that we were able to deliver a quality performance away from home against tough opponents.
"We return to Ireland this weekend with renewed confidence and determination.
"We work a lot on our defence. Last week there were a couple of fairly intense training sessions and that was transferred into the game."
And while Townsend is determined to see Glasgow Warriors go one better this season, he believes just reaching the last four can be considered a success, considering how competitive the RaboDirect PRO12 is this year.
"It was a really competitive league this year. There were six or seven teams chasing those four places two or three weeks ago," he added.
"The way we have played at times has blown us coaches away.
"It all comes down to the effort and fight the players have for each other."
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