Ordered an Adaptec 1420SA RAID card for my Debian Squeeze media server but didn't check to see if it was compatible, turns out it's not because it uses something called hostRAID which requires special drivers that aren't available for Debian. Could I still use the card as an ordinary controller and just use OS software RAID??
I'm not looking for speed, just need to mirror some drives that will be used for storage, the OS will reside on a disk connected to the server's onboard controller so the system won't be booting from any drives on the Adaptec controller.
You still should be able use the 1420SA at least as a usual SATA controller - it's driving chip (Marvell 88SX6541-BCZ) is supported by the kernel.
Even in "host raid" (aka fakeraid) mode you might check out if you can get dmraid to work with it, but usually it is not worth the trouble. You perfectly could set up a redundant md device and write the bootloader to both disks (I believe this is even supported by the Debian text installer) to achieve a very similar result with standard Linux tools which are independent from the storage controller.