I have a 2009 Mac Pro 8-core and I recently bought a Pro Caddy 2 from TransIntl, firstly the power cable didn't work, so they had to send me a new one which took an extra 10 days to arrive.

Yesterday when the new power cable arrived, I plugged everything in and it worked straight away, so I formatted both drives and set them up as a Mirrored Raid Set (The PCIe SATA card is in Slot 4). These drives were now (almost) exactly the same set up as internal drives 3&4

Capture Scratch (Internal)
Format: Mac OS Extended (Journalled)
Owners Enabled: Yes
RAID Block Size: 256

Capture Scratch 2 (Pro Caddy 2)
Format: Mac OS Extended
Owners Enabled:Yes
RAID Block Size: 256

I copied a file to it and everything went well, I Then configured it to hold all the render files etc (everything except Capture Scratch) from FCP and as soon as i started editing, i'd get the beach ball for around 20sec before i could play a heavily render intensive edit i am working on.

I then did some tests with Drive Genius and AJA System Test and...

Capture Scratch
Average Read: 120 MB/Sec
Average Write: 110 MB/Sec

Capture Scratch 2
Average Read: 1.1 MB/Sec
Average Write: 88 MB/Sec

...so my problem is i have 230gb on a drive that I can only read at 1.1mb a sec.

PCI Slot 1 has a link width of x1, While Slot 4 (Graphics card) has x16, if that would have anything to do with it, but from what i've read that should be more than enough bandwidth to handle the data rate.

Does anyone have any suggestions? as to how to get the Caddy working properly? Many Thanks.