Western Digital WD153BA and 205BA
The drive's performance decreases quite evenly over the medium. It provides 22-25 MByte/s within the first 5 GBytes, 21-24 MByte/s between 5 and 10 GBytes and down to 16 MByte/s in the last sector.
I was quite skeptical when I saw the performance drop at ~ 2 GBytes. There is obviously some driver issue giving the benchmark this incredible performance drop. My hard drive contained approximately 2.1 GBytes of data, so all benchmarks were running in the area where this performance drop is supposed to be. As there were no issues with the real world benchmarks, I do not believe in this result.
The 20 GByte drive gets a similar graph as the 15 GBytes model.
There's also a similar effect with the 20 GByte drive. The graph tells us about a performance drop at approx. 12% of the drive's capacity which simply is not there at all.