> what is a Cache Hard(or Solid) disk drive ?
There's no such thing as a "cache drive", at least not something you could go out and buy. There are drives with RAM caches, and you could put cache files onto a drive (the Internet Explorer cache, for example), but the drive itself is just a storage device.
"Cache" is a computer industry term that means "keep a handy copy of the data I just read on some fast storage device that lets me get it back much more quickly than I could if I had to re-read it from it's original source". The CPU (and disk drives themselves) cache disk data in RAM because RAM is faster than the disk. Software often caches data from remote locations (such as the Internet) on disk because disks...