IBM

(IBM) - Get Report

continues to lead the market for server computers, particularly in the hot new category known as blades, a market research company reported Wednesday.

IBM's revenue from sales of servers grew 6.3% year over year in the third quarter, giving Big Blue a market share of 31.7%, according to International Data Corp., a Framingham, Mass.-based market researcher.

As expected,

Hewlett-Packard

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remained in second place, having grown its server revenue by 2.9% in the quarter. H-P's share of the market slipped a bit to 26.8%, from 27.5% a year ago.

Overall, revenue in the server sector grew by a rather sluggish 5.5%, although IDC research manager John Humphreys said that the slowdown was seasonal and that he expects stronger growth in the December quarter.

The report gave more evidence of the increasing commoditization of the server market, once the province of high-end machines running proprietary versions of Unix.

Revenue from servers aimed at the mass business market, called "volume servers" by IDC, grew by 18.2% year over year. And Linux servers posted a ninth consecutive quarter of double-digit growth with year-over-year revenue growth of 42.6% and unit shipments up 31.7%.

Unix server revenue dropped 2.3% in the quarter.

Similarly, revenue derived from blade servers, essentially a compact server contained on a single circuit board that shares a power supply and other components with additional blade servers in the same chassis, grew by 44% year over year and 22.5% sequentially, IDC found.

IBM and H-P continue to

dominate that market segment; IBM with a share of 44%, while H-P has a 38% share.

Cash-conscious information technology managers have increasingly turned to blade servers because they are relatively cheap and easy to maintain, and they save space.

Dell

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, the world's leading PC maker, grew its server revenue by 14% and added more than a half-point to its market share, which now stands at 10.1%.

But Dell has yet to register much success in the blade server business, said Humphrey, estimating the Round Rock, Texas, company's share at less than 5% of the market.

Server revenue for

Sun Microsystems

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was essentially flat year over year, and the struggling company lost a half-point of market share, slipping to 10.2%, barely ahead of Dell.