This may be the year that blade servers finally cast off their bad rap. Introduced in 2001, blade servers were supposed to change the computing landscape, but questions about reliability, power consumption and heat output put a damper on adoption.

However, with HP and IBM focused on improving the form factor, and Dell and Sun reentering the market, blades are getting a second look.

In a recent report, IDC analysts called server blades "a growth driver" in the fast-expanding x86 market. Shipments of blade servers grew 52% in the United States in 2005 compared with 2004, as customers worldwide spent $2.2 billion on the systems, a jump of nearly 81% compared with 2004, according to IDC.

Blades accounted for a small fraction of the overall server market a few years ago, but IDC estimates they will account for 11% of the market this year and about a quarter of the market by 2009.

Part of the reason for the growth is that vendors are making the systems more capable of supporting important business applications. IBM, for example, earlier this year introduced its BladeCenter H chassis with support for InfiniBand and 10G Ethernet.

In addition, IBM announced new blade servers, including a low-power Xeon blade, aimed at appeasing buyers concerned about the heat output associated with packing numerous small systems into tight spaces. Egenera also targeted those heat concerns when it introduced in January a cooling unit called the CoolFrame for its blade-based systems.

Meanwhile, HP last week introduced its next-generation blade servers, the Blade System c-Class, which includes enhanced technologies around virtualization, networking, power and cooling, and systems management. Sun, which scrapped its product line last year, also plans to reenter the market with Operton-based blades coming soon, Sun executives say.

"Today customers have to make a number of compromises when deploying blades, compromises in I/O throughput and other capabilities. There also are some complexities in managing blades," says Graham Lovell, senior director of x64 systems at Sun. "Expect our next generation of blades to remove those hurdles. We plan to make our blades look more like standard servers."

A growing number of enterprise customers are finding benefits in blade offerings. Aegis Mortgage in Houston, for example, decided to standardize on blades about a year and a half ago as a way to deal with data center space constraints.