Reason for See-saw in HD Tune? (Raid 0)

I've got 3x500GB HDD in Raid 0 (Stripe 128k) on GA-P67A-UD3R-B3 and got this with HDTune - is this normal?:



Here's the crystaldiskmark:



I tried installing the Intel Rapid Storage drivers stuff from the motherboard CD but it would result in windows hanging on restart so that was uninstalled.

 

Looks like you're hitting some kind of ceiling. Usually a benchmark of a mechanical HD (including RAID arrays) will show the fastest speed at 0% on the x axis, then taper off as the head moves further inwards (as the tracks get smaller in diameter the reduced density means a slower raw read/write speed). With your graph, although it's see-sawing the speed is still pretty much the same at both the start and finish, which means something else is causing the bottleneck.

The difference in your hdtune and crystaldiskmark benchmark speeds, and write being mostly faster than read for the latter is definitely odd too.

What HDs are you using?

 

yeah, I thought the same thing - but other benchmarks seem to be ok (are there any other hdtune style ones? - hdtach doesnt work on win7 x64)

writes often faster due to write cache possibly.

hdd are st3500418as i think (500gb, single platter, 7200.12 seagate)

 

this is 2x 500g re4 raid0 western digital hdds in raid 0(128k stripe)
on a gigabyte ud5 1366 (quad 3g cpu)


xp pro sp3 write cache=on