What did you set for your stripe size? I have very very similar results with 2xWD 160gb SATA drives and I set a stripe size of 64k. Thinking of trying 32k to see if I can get more performance. I've read that stripe sizes have ALOT to do with overall read/write rates of a RAID 0 config, but I can't say I'm positive based on personal experience as this is my first foray into RAID setups.
From what I've read it depends GREATLY on what you intend to do with your raid setup. Larger stripe size for larger files. (Video encoding, Audio Rendering, etc...)
Smaller stripe sizes for gaming, games have alot of smaller files that need to be loaded such as interfaces, addons, etc... and a smaller stripe size means the data gets split amongst two drives instead of one drive taking a single small file... I'm half tempted to image my drives and reformat with a different stripe size to see how it effects transfer rates.
Yea there kind of old drives that where bargain drives to begin with i play on upgrading..some day when i have the money, (currently building my new system as the parts come in 17yrs old without a job is a terrible place to be when you have an addiction to building/serving/improving computers...=P)
and a smaller stripe size means the data gets split amongst two drives instead of one drive taking a single small file
...causing lower performance. For a good RAID implementation, there is no advantage in taking a small stripe size; it will only cause parallellism to be lost because now 2 drives have to handle 1 I/O request, and their seek times take up most of the time required to finish the operation; so picking a low stripesize lowers the performance on small I/O operations.
On very bad and rudimentary fake RAID implementations, the driver does not support reading anything less than a stripe block, so if you set it to 128KiB and you only need to read 4KiB, the driver will read the rest anyway. Proper implementations will allow any part of the stripe block being read, and as such a stripe block cannot be too low. 1MiB might also be a good value, but often only supported on software implementations.
@Topicstarter: could you please post results with a proper filesystem benchmark, such as ATTO? The way HDTune reads from the device (q=1) may cause it to show lower numbers than you're actually getting via your filesystem (which uses q>7 on sequential transfers). If you don't yet have ATTO you can get it here: http://www.fluffles.net/files/ATTO-256.exe