Raid 5 performance issue. What gives?

[theorem7]

I have a built-in intel raid controller with 3x500gb drives in a raid 5 configuration, which I've been using for about 18 months. Recently, the array developed some pretty severe performance issues--games pausing every couple of seconds to load, stuttering HD playback, etc.

So I ran HD tune and got the following results:

As a control, I ran the same tests on my old 36gb raptor and got this:

To preempt an obvious question, the array is not rebuilding or verifying.

I thought fragmentation might be the issue, but the built in windows defragmenter and diskeeper are both reporting very low levels of fragmentation.

Has anyone encountered this before or have any thoughts about what this weird variance in performance might be attributable to?

<edit: my apologies, I seem to have posted this in the incorrect forum>

 

[Mir96TA]

There are some key info which is missing
For example what controller/Chipset you have ?
What are excat Model # of the HDDs
What OS ?
Here is a example of my 9ICHr with 3 WD which is basically WD5001AALS
They running off P35 Chipset with Xeon 3110 CPU

In Raid 0 they perform like following

In order to have a Kick Arse performance you would following ingredients
Raid card with Cache memory (More is merier) Chipset which has some thing like XOR processing engine for example Intel's IOP333 chip.
On HDD make sure you have function TLER (WD) ERC (SeaGate) CCTL (Samsung). Other wise HDD may have to resend the Data few times if it get error out.

 

[Emulex]

do you not have the option to verify and repair the array? its on one of my old 975x ich7R - you just click verify ( or verify and repair) and it does a sweep looking for errors on demand and works it out - i do it about every few months and it finds a few sectors.

i noticed one of my newer pc's does not have this option at all.