News of the pending fund close was first reported today by The Wall Street Journal, and later confirmed by Fortune. [Update: One could reasonably argue that Reuters got it first, more than a month ago]

Blackstone (BX) will make its final investment — or investments — out of its $21.7 billion fifth fund within the next month, after which it will begin deploying the new vehicle.

If all of this sounds like old news, that’s because it is. Sort of.

Blackstone originally began raising this fund in October 2007 with a $20 billion target capitalization. For chronological context, that was nearly one year before Lehman Brothers filed for bankruptcy. The subsequent financial collapse caused Blackstone to reconsider its plans, particularly as many of its prospective investors — particularly large state pension funds — began to suffer the ills of illiquidity.

A reduced target of $15 billion was set, but even that figure seemed overly ambitious. Blackstone spent more than a year stuck at around $9 billion, with internal sources saying the real hope was to hit $12 billion.

Following a portfolio rebound — thank you, Freescale — Blackstone president Tony James said during a June 2010 media call that new investor interest meant that the fund would close at $13.5 billion. Actually, he said the fund was closed at $13.5 billion, but a spokesman later said that James had misspoke.

So now we’re back at $15 billion, or the original target revision. I wrote in June that Blackstone would raise “the year’s largest and most underwhelming private equity fund,” due to its inability to meet initial expectations. But given how low the firm had reset its targets, I might need to reconsider…

This is easily the largest private equity fund raised since the crisis began, even if it took a tortured process to get there (the length of fundraising is typical for BX, the downward target revisions are not). And it also is likely to serve as some sort of benchmark for rival Kohlberg Kravis Roberts & Co. (KKR), which next year plans to formally launch fundraising for its next North America-focused fund (although KKR would view $15 billion in the aggregate, since it also has Europe and Asia-focused funds).

There also are press reports that Apax Partners is seeking to become the market leader with a $16 billion vehicle, although I honestly cannot imagine Apax being able to climb that mountain.

Expect Blackstone to make its final investment out of its $21.7 billion fifth fund within the next month, and then to begin deploying the new pool.