airjrdn

I ended up biting the bullet on a 3rd cage and SATA card last week.  I had a couple extra 2TB drives and one 1TB drive lying around and wanted to get them added to the pool.  Total usable storage now sits at 19.1TB.  I've since enabled 3x duplication on almost everything and DrivePool is in the process of working its magic.  I love that software!

I had maxed out my nearly 4 year old 8-bay Calvary enclosure (EN-CADA8B-SD) with 2TB drives and was beginning to have issues somewhere in the storage chain (eSATA port multiplier card, drivers, eSATA cables, Calvary enclosure, etc.).  After troubleshooting off and on for a couple weeks or longer, I was ready to replace it with something less problematic that wasn't limited to 2TB drives.  I didn't however want to spend half a grand for something that came with RAID functionality I knew I'd never use.  For the time being, I wanted to continue using my existing drives and just replace the enclosure and connection to it.
 
The enclosure was hooked to a Dell Inspiron 3847 (4th Gen Core i7, 16GB, running Win 8.1).  Duties for the machine include Plex, Subsonic, DNS updating, Crashplan backups, Syncback backups from the web, and of course, storage.  The machine sits out of sight in the basement, so going with something less pleasing to the eye was fine.
 
I ended up going with a pair of Rosewill 4 drive cages and a couple of IO Crest SATA cards for connecting them to the Dell - which only has 2 PCI-e x1 slots and a single x16 slot.
 
$45 for each of the Rosewills, and $34 each for the IO Crests and I was almost ready to go.  The Rosewill cages came with SATA cables that were long enough to reach from the inside of the case to the cages sitting right behind the Dell.  Power to the cages was supplied by an extra power supply I had lying around.  A quick short from the green wire to any black one will make the power supply think it's hooked to a motherboard and power on.  I used a paper clip to accomplish that.  If you go this route, keep in mind you'll need about 10w for each drive to be on the safe side for power requirements.
 
If you're interested in doing something like this, what you get is four drives worth of connectivity for about $80.  There's no port multiplier functionality going on, one drive connects to one port on a card.  If you have extra SATA ports, you can skip the card purchase.  If you have extra molex power connectors for the Rosewill cages, you can go a little less ghetto than I did and skip the power supply lying on the desk.
 
You are limited in performance to what a PCI-e x1 slot can handle (about 240MB/sec if I remember correctly), which seems fine, but remember, you're running four drives off of that, and 240MB/sec is theoretical.  Real world performance will be lower.
 
All in all, I definitely consider it a win.  For not much out of pocket, I replaced the Calvary, gained the ability to use larger drives, and also the ability to buy another card and cage for a total of 12.  Not bad for an initial outlay of about $160 out of pocket.
 
Hope this helps someone out there looking to do something similar.
 

pclausen, would you be willing to detail out your hardware?  I'm just curious about how you have that many drives connected, cards/connectivity type used, if you'd do things differently a second time around, etc.
 
Thanks in advance
 

I ended up biting the bullet on a 3rd cage and SATA card last week.  I had a couple extra 2TB drives and one 1TB drive lying around and wanted to get them added to the pool.  Total usable storage now sits at 19.1TB.  I've since enabled 3x duplication on almost everything and DrivePool is in the process of working its magic.  I love that software!

Crashplan isn't going to offer duplication, it's backup software, not syncing software. The advantage (one of them anyway) of backup software is versioning.  You can get back different versions of your files.
 
If you simply want to sync a copy of your pool or some subset of the files on it at different intervals, look into Syncback, FreeFileSync, etc.  I've used others, but none with the simplicity and robustness of those two.  I use Syncback for automated syncing, and FreeFileSync for one-offs.