Mac Pro Raid Setup

• What kind of throughputs (speed, say in MB/s) do you need?
• File sizes you typically generate?
• Actual software used, and how do you use it (layers, ...)?

I ask, as such details are important. I also realize that with the existing RAID card (garbage BTW), what can be done is limited.

The best you could do is:

1. Use the ODD_SATA ports on that particular board for both a separate OS/applications disk (HDD will give you more capacity), and a second separate disk (SSD would be the fastest, say 40GB unit from OWC) for scratch. Please note, that in your system, the ODD-SATA ports can only boot OS X (will not boot Windows or Linux).
2. Then add the 4th disk in the HDD bays to the RAID 5.

Added cost would be ~$200USD, as you don't need 2TB for OS/applications (based on $100 for the SSD and $100 for the mechanical OS/applications disk).

Past this, you'll need to get a different card, drives (should be using enterprise grade HDD's on a hardware RAID card), and possibly external enclosure/s (more members = more speed due to the added parallelism).