Forecast highlights spread of the operating system, a relatively new rival to Unix versions such as Solaris and to Windows.
Revenue from Linux servers is expected to grow annually at 22.8 percent, compared to 3.8 percent for the overall server market, IDC said.
In addition, Linux servers should account for 25.7 percent of server unit shipments in 2008, up from 15.6 percent in 2003, IDC said.
The results highlight the spread of the operating system, a relatively new competitor to Unix versions such as Sun Microsystems' Solaris and to Microsoft Windows. The top four server sellers--IBM, Hewlett-Packard, Sun Microsystems and Dell--all support Linux, though Sun steers customers to Solaris. The top sellers of Linux and accompanying software are Red Hat and Novell.
IDC also said Linux is disproportionately popular for blade servers--thin systems that plug into a chassis with shared networking and power infrastructure, and a fast-growing part of the overall server market. Linux is used on about half of blade servers today, compared to 20 percent of rack-mounted servers and 11 percent of free-standing servers.
IDC also said Linux is now most often used on dual-processor servers instead of single-processor machines, an indication that it's running more important tasks on more powerful machines. Single-processor machines are the second most widely used option, followed by four-processor systems.
Linux also can be run as a partition on powerful machines such as IBM mainframes, Power processor-based servers and on Hewlett-Packard's Superdome servers.