Western Digital Caviar Green, 1.5TB: WD15EADS
The 1.5TB model from Western Digital differs from its larger cousin with a considerably lower price (but the Samsung is even cheaper as yet). Like the 2TB model, this HDD comes with 32MB of cache only.
If you take a look at the official specs, you can note that this model weighs as much as the 2TB model. So, it is quite possible that this HDD is based not on three full-featured platters but on four reduced-capacity platters (or has disabled heads). This would be a reasonable solution. If there are few 500GB platters as yet and the product yield is rather low, why not format the rest of the platters for a lower capacity? Considering this drive’s IOMark results, we write four platters and eight heads into its specs. We can change our opinion if we see any evidence to the contrary.
Western Digital AV-GP, 2TB: WD20EVDS
Western Digital tried to make the most from its early coming to the 2TB sector. So, after the desktop series, the AV-GP series was expanded as well. The key feature of this series is special firmware which is optimized for simultaneous delivery of up to 12 HD-video streams. Some time ago we tested a special-purpose disk (that was the 1TB Seagate SV35.3) and its performance did not impress us at all. Perhaps this one will do better.
Western Digital claims the AV-GP series to use special PWL technology (Preemptive Wear Leveling). Its point is that the HDD moves its heads above the entire platters from time to time. The company claims this helps reduce the nonuniform wear of the platters typical of HDDs that are employed for video applications. Unfortunately, Western Digital does not reveal all the details and we don’t really know how the wear of the platters can be affected by the actuator with heads sweeping over the platter surface. Perhaps the heads are working at that, reading and writing data back?