For backups and external storage, I use a Wiebetech RTX400-SV connected to a Sonnet Tempo SATA E4P PCIe card in my Mac Pro, which is running Mac OS X Snow Leopard 10.6.2. Today, I connected two new 2TB SATA drives and tried to create a RAID 1 (mirrored) volume with 256K block size (for video). My Mac Pro immediately kernel panicked. Upon rebooting, I discovered that if I connected either of the drives in the RAID 1 volume, my Mac would immediately kernel panic. Not good.
To recover, I had to connect the drives using a second Wiebetech enclosure to another machine, an iMac, which uses a Firewire interface to the drives. I re-partitioned the two drives and created a RAID 1 volume with the default 32K block size, and all is working now.
**UPDATE**: Note that I *could* successfully create a RAID 1 volume with 256K block size on the iMac via Firewire, but it resulted in a kernel panic as soon as I plugged the drives into the Mac Pro via eSATA. A RAID 1 with 128 block size seems to work fine, and is what I have settled on using.