RAID and Seagate Barracuda ES.2 ST31000340NS: slow writes

An Interesting Problem:

I am installing the Seagate SATA ST3500320AS in a WinTel system running the Intel D865GBF motherboard (firmware revision P25), and no other expansion cards. The machine is a stand alone file server, running Windows Server 2003 with current patches.

Installation steps: physically install drive into unit. Leave Hard Drive jumper installed limiting data transfer rate to 150MB/s. Start unit. Using Physical Drive utilities in Windows Server, create a partition. I did not use the wizards' tool to format the drive.

From a command prompt, I formatted the drive using the command:

format d: /u/fs:ntfs/a:512

The format completed successfully.

USAGE AND FAILURE
I loaded the drive with data, and attempted to fill the drive to capacity (465GB). Drive performed fine until we reached ~ 120GB of capacity, and then the drive performance went to zero.

Specifically, using the Microsoft Performance monitor, I viewed the %ReadTime, %WriteTime, and AvgDiskQueueLen for the drive. When operating normally, these values fluctuated around small values, indicating good performance.

When the problems occurred, the %DiskWriteTime jumped to values beyond 2000, and the AvgDiskQueueLen value remained up around 18.

Attempting to reformat this drive using the default cluster size also produced the same results:

format d: /u/fs:ntfs

Any ideas why this is happening?

THANK YOU!