A server glitch caused the Dow Jones industrial average to drop about 200 points in less than a second yesterday. According to the Associated Press:

Dow Jones & Co., the media company that manages the well-known index of 30 blue chip stocks, said it discovered shortly before 2 p.m. that its computers weren’t properly handling the day’s huge volume in trades at the New York Stock Exchange.

It switched to a backup computer, and the result was a massive swoon in the index as the secondary system took over processing shortly before 3 p.m.

It looks like the plunge was caused by a backup of orders that suddenly registered when the backup server took over. Kenneth Polcari, a longtime stock trader, told Bloomberg: “The technology issues created some anxiety, which exacerbated the market’s move.”

You would think the Dow Jones would know how to handle a surge in traffic without messing up the industrial average, but apparently even they struggle with high availability.