Actually, you can run raid mirroring with 2 disks, md devices will function on partitions, so we have set up storage servers with :
disk1: small root partition and large data partition
disk2: (unmounted) copy of root partition on disk1 and data partition equal in size to the data partition on disk 1
the 2 secondary partitions are set up as a raid mirror.
The beauty of this is if the primary disk fails, you can boot from a floppy and restore using the secondary root partition.
This sort of configuration is easy to set up when installing Suse, and I assume, Redhat or Mandriva.
There are several howtos on the net, but if you want to run striping with a hot spare, you are best using a dedicated controller card.
We have used an Adaptec PATA Raid card for that setup (4+1) on our redhat 7.3 server, and it performs pretty well, and the linux support is OK, although SATA might be the way to go.
Other than software raid, be aware that some Motherboards have SATA or IDE raid controllers which are really software based, and will often only work with windows.
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