The radius servers at my work take a pretty substantial beating. We're what's known as an ISP aggregator. We provide modem services for many dial ISPs and this means we have lots of Cisco access servers with thousands of modems in each chassis. Growth has been good, and the old Pentium III Linux systems with Freeradius and MySQL accounting were buckling under the load.
We found a keenly priced bare-bones server with a dual Xeon motherboard and a four disk SATA backplane. It claimed Linux support so we ordered a few. Turns out the SATA controller is an Adaptec HostRAID 8110 - BIOS software RAID, for which there were binary-only drivers for a couple of old RedHat and SuSE kernels. Not good.
Some (non trivial) investigation led me to the understanding that this particular HostRAID junk was based on the Marvell chipset, and that Abit had indeed recently released some source code. This chap had beaten that code into submission and produced a useful little HowTo for Fedora FC3.
There's no floppy drive on these boxes, so the process is a royal pain in the fundament. I used a USB floppy drive, which Linux sees as a SCSI removable disk. The trick is to force anaconda into pausing before it builds the device tree so that you can load the kernel module. This is done by not having a mouse installed. Switch screen, make a device node for the USB floppy, mount it, insmod and away you go. A little more fiddling to fdisk up the partitions before using disk druid to make the raid disk and volumes. Once installed, build up the ramdisk, and configure up MySQL and radius.
Not so bad... except I had to build a half dozen of them fairly rapidly. Nearly twelve hours later, and I have a batch of RAID-5 dual Xeon servers running a patched Fedora Core 4 with MySQL and FreeRadius.
The key here is to avoid Adaptec HostRAID if you can, and if you cannot, understand that its likely just some flavor of the Marvell SCSI-SATA bridge firmware (though more than one thing goes by the same name).