The HDWE140 4GB drive is advertised as a hybrid drive, and is definitely not an SSD drive. When I try to benchmark this drive Defraggler crashes. Looking at the map that comes up, it seems that something rearranges the disk blocks so that all the free space is at the end. However I can not see if there is any fragmentation. I needed to have a large contiguous space for Photoshop cache storage. Strange, I just tried Defraggler Benchmark on it and it worked! It also showed an almost perfectly defragged drive with only 1 block with fragmented files. I suspect that the drive does its own defragging.
