The biggest winner here is Atlas Venture, which first invested in Isilon back in 2001 (at a pre-money valuation of just $7m). The firm didn’t sell shares in the company’s December 2006 IPO ($13 per share), which looked like a good decision when the stock experienced a 77% first-day pop. Then it looked like hubris, when the shares began to tank.

If you include a pair of small share sales in Q2 and Q3 of this year, Atlas will return a total of $473 million on Isilon. It’s the largest cash return in firm history – the 20x multiple was topped by some dotcom-era exits — and is a vital boost for a firm that many wrote off after fundraising troubles and personnel bloodletting.

Actually, speaking of that latter point: The Atlas partner on the deal was Barry Fidelman, who transitioned into a venture partner role when the firm restructured in early 2009.

My initial thought was that this looked similar to what happened at Charles River Ventures, which sidelined the partner responsible for EqualLogic (before that company was bought by Dell for $1.4 billion). But Fidelman went part-time of his own accord, largely due to his advanced age (he’s 70, despite some recent forays into ski-jumping and snow-boarding), and desire to be more of a coach than fulltime due diligencer. So mark this down as a feather in the cap for Atlas’ old guard.