Advent International, a Boston private equity firm, has raised a $10.8 billion buyout fund, the largest of its kind launched since the 2008 financial crisis. The fund will invest in mid-size buyout deals. It raised about half the money from large investors in North America; the other half came from Europe, Asia, and the Middle East, said managing partner David Mussafer.

It took eight months to raise the money, which Mussafer called a success, given “There’s a belief that, overall, the available capital for private equity is down 50 percent.”