Contact Red Hat technical support personnel for assistance.
We ran the same test on a peer vendor's storage device, and the same symptom occurred.
It is concluded that the significant storage performance fluctuation was due to an inherent mechanism defect on the Linux rhel5u3_x86-64 2.6.18-128.el5 application server.
Storage performance fluctuates when the rhel5u3_x86-64 2.6.18 operating system and the ATTO-FC82EN HBA are both used in a SAN network environment. Performance-demanding services such as VOD do not fit in such an environment.