Virtualization has recently come under the spotlight as an important emerging technology. The technology was initially focused on services rather than the effective use of the system when it was developed in the 1960s. Now, following with technological advancement, virtualization is used on servers based on x86. The biggest merit by far of this technology is economic. Virtualization enables server integration, which can cut operating expenses (including personnel expenses) since it costs less to purchase, power and maintain multiple servers if they are integrated by the virtualization technology. This study examines the trend of virtualization technology and suggests a roadmap for future server integration.