Alan,
You make a very interesting assessment of external PCIe. It's a little bit of a conundrum if you think about it. If you were to use eSATA, you would have to add a SATA card to your PCIe bus.
But where the real advantage of speed comes, is from the RAID itself. I'm going to over simplify, but let look at the HDPro. It has 8 SATA II drives. Each have a bandwidth of 3Gbs. Now the drives themselves are not that fast. But when you add 8 together in a TURE hardware RAID (independent CPU and cache) you are able to achieve speeds that are almost double the bandwidth of the SATA II bus.
To get all of this supper fast data to the computer you need a fat pipe. Fibre has been used by other companies, but the catch is that this high throughput is close to it's maximum bandwidth. With ePCIe you have 20Gbs. That leaves plenty of overhead.
So in summary the type drives used in the RAID become irrelevant. SATA II drives are fast and affordable, which is why they are used. You could use SAS drives in the same fashion and achieve even greater speeds, ePCIe allows for that overhead.
The cable type and length does vary between ePCIe and eSATA. Also the ePCIe connection is a lot more substantial than eSATA. I also find eSATA to be flakey while ePCIe is rock solid. But the major advantage is the speed difference eSATA 3Gbs and ePCIe 20Gbs. You just can't have a RAID that runs at 400+ MBs over an eSATA connection.
Jared PicuneIdea Spring Editing, Inc. Denver Final Cut Pro UGGeeky Mac | FCP Tips & Tricks
