David,
Here are some things to think about when considering RAID 1 options.
- Most onboard IDE/ATA controllers were not designed for fault tolerance. If you put both drives on the same controller (master/slave) failure of one drive will most likely render the other drive inaccessible to the controller. Thus you really need one controller per disk. In addition, even in a one controller per disk situation a drive failure could also make the controller fail and bring the whole box down.
- Until recently you needed some mojo to make your root partition RAID with software RAID. I think late versions of lilo/grub/linux kernel support root on RAID.
- If you decide to go the hardware route, Promise does make some cheap ATA RAID controllers that do "almost" hardware RAID. A lot of the work is done in the driver software, but still the whole array is presented to the kernel as one device. I have a couple of these and they work OK. What I've never investigated is if the driver presents an interface in /proc that would let you monitor the status of the disks. The Tech Report did a really in-depth review and analysis of different hardware IDE RAID controllers--it is here.
- "Good" RAID 1 implementation should improve read performance since technically data can be read from two drives at once (unless the array is missing a disk). I remember rumblings on the linux-raid list that the RAID implementation does do this; I don't know about hardware solutions.
- Hot swapping of IDE disks is not available unless your controller supports it and you have the right IDE cages. The IDE electrical spec was never designed for hot swap, so be careful when choosing hot-swap cages.
- 3ware cards are the acknowledged leader in IDE RAID. They can be expensive, but offer all of the features of a SCSI solution (hot swap/hot spare). Good Linux support too.
I have been looking at IDE RAID options for some time. Since IDE disks do not come in more than 7200 RPM version yet but I can get SCSI at 15000 RPM an IDE solution will probably not reach the performance of a SCSI option. You're looking at probably half the cost for IDE though, and more total storage with less hardware since you can get 250 GB IDE disks. In the end we will still go with SCSI I think.
