Hardware RAID?
If you are interested in hardware RAID get this:
1) areca ARC-1882IX-12 PCI-Express 2.0 x8 SATA / SAS (Serial Attached SCSI) 16 Ports 6Gb/s SAS/SATA RAID Adapter
2) Stardom ST5610-4S enclosure
I have a MacPro early 2008 2.8 octocore as you do, and I did much research. You use 4 of your drives in the internal bays and connect the areca's internal SAS connector to the mac's SAS connector.
Buy four more drives and stick them in the Stardom enclosure. Set your RAID to 1+0. That way you can stripe your internal drives in RAID 0 and have the external enclosure RAID 1 your internal drives. You would have a lot of redundancy and you should be able to achieve at least 400 MB/s sustained read/write speeds with your SATA III drives. (did I forget to mention you need to connect the external SAS port of the ARC 1882 to the SAS port of the external enclosure?)
You never mentioned how much resources/funding you had, but the ARC-1882 is a screaming RAID card. If you put four OWC 6G SSDs in a RAID 0, you will have sustained speeds of over 2000 MB/s. By the way, you can do that since the ARC-1882 does have a lot of internal SAS connectors (it's pretty easy, one SAS can feed 4 SATA III connections).
This whole set up will set you back about $2000.00 US, but hey, you will truly have a super fast rig since it's the hard drives which slow down even the newest machines the most.
Good luck -- the set up above is my set up, and it will boot since Areca supports MacOSX (load the drivers from their website first before you create the array). And as everyone has told you already, you will need preferably an external Firewire drive with an exact copy of your current boot volume so you can copy it back to the array (Carbon Copy Cloner is free and it will make copying your boot volume easy)
If you are uncomfortable having your array as the boot drive, you may want to consider putting a SSD drive in one of your empty optical bays and connecting it to ODD eSATA port number 5 or 6 located in the MacPro. You can have the Mac boot from that SSD drive and use your array as the scratch disk. You can Carbon Copy Cloner back up your SSD drive to the array once in a while so that if you have a failure of your boot drive, you could possibly boot your computer from the array instead.
Go to http://macperformanceguide.com/Mac-InstallingSSD.html to see how you can do the SSD installation. It is not easy, but it is cheap (except for the cost of the SSD itself!)
My current set up is overkill for our office, but then again, failure is NOT an option.
If you are interested in hardware RAID get this:
1) areca ARC-1882IX-12 PCI-Express 2.0 x8 SATA / SAS (Serial Attached SCSI) 16 Ports 6Gb/s SAS/SATA RAID Adapter
2) Stardom ST5610-4S enclosure
I have a MacPro early 2008 2.8 octocore as you do, and I did much research. You use 4 of your drives in the internal bays and connect the areca's internal SAS connector to the mac's SAS connector.
Buy four more drives and stick them in the Stardom enclosure. Set your RAID to 1+0. That way you can stripe your internal drives in RAID 0 and have the external enclosure RAID 1 your internal drives. You would have a lot of redundancy and you should be able to achieve at least 400 MB/s sustained read/write speeds with your SATA III drives. (did I forget to mention you need to connect the external SAS port of the ARC 1882 to the SAS port of the external enclosure?)
You never mentioned how much resources/funding you had, but the ARC-1882 is a screaming RAID card. If you put four OWC 6G SSDs in a RAID 0, you will have sustained speeds of over 2000 MB/s. By the way, you can do that since the ARC-1882 does have a lot of internal SAS connectors (it's pretty easy, one SAS can feed 4 SATA III connections).
This whole set up will set you back about $2000.00 US, but hey, you will truly have a super fast rig since it's the hard drives which slow down even the newest machines the most.
Good luck -- the set up above is my set up, and it will boot since Areca supports MacOSX (load the drivers from their website first before you create the array). And as everyone has told you already, you will need preferably an external Firewire drive with an exact copy of your current boot volume so you can copy it back to the array (Carbon Copy Cloner is free and it will make copying your boot volume easy)
If you are uncomfortable having your array as the boot drive, you may want to consider putting a SSD drive in one of your empty optical bays and connecting it to ODD eSATA port number 5 or 6 located in the MacPro. You can have the Mac boot from that SSD drive and use your array as the scratch disk. You can Carbon Copy Cloner back up your SSD drive to the array once in a while so that if you have a failure of your boot drive, you could possibly boot your computer from the array instead.
Go to http://macperformanceguide.com/Mac-InstallingSSD.html to see how you can do the SSD installation. It is not easy, but it is cheap (except for the cost of the SSD itself!)
My current set up is overkill for our office, but then again, failure is NOT an option.
The drive's controller will step down to SATA II (which it won't be able to saturate, so don't worry about this).