Running eSATA drive with single cable from laptop

My Dell Latitude E6520 has a combo eSATA/USB port. They make SATA drives with external enclosures that should be able to hook up to this kind of things. USB, by spec, carries power. It seems reasonable that I should be able to get a cable and an enclosure that grab that power and push it to the drive while carrying data at the same time. Easier said than done.

Tried this combo:

• Dell Latitude E6520
• Star Tech "infoSafe" silver power eSATA to SATA external hard drive enclosure (S2510PESAT) - $25
• Aleratec Power over eASATA cable (X0003ZRM9F) - $12

Initial connection shows now power when using just the eSATA cable and enclosure. However, if I connect the funky USB pig tail, then the power comes on and it works. After investigating with StarTech and Alertec, I came to the conclusion that the cable wasn't correct. Alertec sent me a replacement cable and magically everything started working. The new (correct) cable had cable ends that were molded with the words "SATA + USB" on them, indicating that it knew it was using USB power. The original (incorrect) cable did not.

Original investigation certainly confirmed that all my concerns with the cable were true. This post (http://forum.notebookreview.com/dell-latitude-vostro-precision/390744-power-over-esata-latitude-e.html) talks about Dell E6500 not directly supporting it, although it supposedly has the "modes" for it. It leads to various places that don't really tell me if things are supposed to work. It also has a link to another thread with some more analysis: http://forum.notebookreview.com/hardware-components-aftermarket-upgrades/349325-esata-external-hard-drive-enclosure-supports-power-combo-usb-port.html 

When I talked to StarTech, they indicated that it should always work if the right cable is in place. The laptop does NOT do anything crazy like disabling the USB power when the eSATA is connected.  Their claims is that their ESATAUSB3 cable should work properly ($25 cable). Thankfully my $12 cable for Alertec worked AFTER they sent me the correct one. Demerits to them for sending me the wrong one the first time.

As another possible solution, there are reports that this $13 drive enclosure from geeks.com works for both AND includes a cable: http://www.geeks.com/details.asp?invtid=HE-2521B&AID=10439518&CJPID=3640576&cm_mmc=CJ-_-2617611-_-3640576-_-Geeks.com_Gifts. The pictures don't necessarily indicate that it has a single eSATA/power cable, so it's tough to tell. 

After hooking things up I determined that  the eSATA connection is about 2x as fast as the USB connection with nothing difference except the cable hookup. I can copy a 3GB file from laptop to external drive in about 60 seconds. The same file over USB takes 120 seconds. Read caching during the USB copying process actually causes it to peak at 100 MBs, then slowly ramp down to about 40 MBs during the first 60 sec of the transfer, but then it freezes at 100% status for another 60 seconds while it finishes writing things. With the eSATA copy, it was a more constant 40-50 MB/s and gave an accurate representation of 100% completion, then finished immediately.