The Linux operating system will account for 29 percent of the worldwide server market in 2008, up from 12 percent last year, according to predictions published by the IDC.

Linux will take $9.7 billion from the $60.8 billion market when measured by revenue within four years, according to the research company. Servers running Windows, meanwhile, will account for $22.7 billion of the market.

IDC also forecasts that the worldwide server market will grow at 3.8 percent per year for the next five years, jumping from $53 billion in 2004 to $60.8 billion in 2008. Growth will be strongest in central and eastern Europe and the Asia Pacific region, both of which are expected to grow more than 6.5 percent, year-over-year, until 2008.

Though Windows will account for just 37 percent of the 2008 server market, when measured by dollars spent, they will account for 60 percent of the units shipped, a slight drop in market share from the 63 percent of units shipped IDC reported for 2003.

Sales of blade systems are also expected to grow rapidly. By 2008, blade shipments will to reach $9 billion, the company says, or 29 percent of server units shipped. Blades accounted for just four percent of the server market in 2003.