Input/Output (I/O) performance is one of the key areas that need to be carefully examined to better support IT services. With the rapid development and deployment of virtualization technology, many essential business applications have been migrated to the virtualized platform due to reduced cost and improved agility. However, the impact of such transition on the I/O performance is not very well studied. In this research project, the authors investigated the disk write request performance on a virtual storage interface and on a physical storage interface. Specifically, the study aimed to identify whether a virtual SCSI disk controller can process 4KB and 32KB I/O write requests faster than a standard physical IDE controller. The experiments of this study were constructed in a way to best emulate real world IT configurations. The results were carefully analyzed. The results reveal that a virtual SCSI controller can process smaller write requests (4KB) faster than the physical IDE controller but it is outperformed by its physical counterpart if the sizes of write request are bigger (32KB). This manuscript presents the details of this research along with recommendations for improving virtual I/O performance.