Raid0 performance degradation?

Not sure if this belongs here or on SuperUser, feel free to move as appropriate.

I've noticed the performance on my RAID0 setup seems to have degraded over the past months. The throughput is fine, but I think the random access time has increased or something.

In use I generally see about 1-5mb/sec when loading stuff in Visual Studio and other apps and it doesn't seem like the CPU is bottlenecking as the CPU utilization is pretty low. I don't recall what Access Time used to be, but HD Tune is reporting 12.6ms Read throughput is showing as averaging about 125MB/sec so it should be great for sequential reads. Defrag daily and it shows fragmentation levels low, so that shouldn't be an issue.

Additional info, Windows 7 x64, Intel raid controller on mobo, WD Black 500GB (I think 32mb cache) x2.

Possible candidates:

• Full NTFS. With space available <10%, NTFS performane suffers, but mostly (not only) for writes
• Internal remapping of sectors of the HDDs. Look at the SMART data.
• File system damage