I currently have an ftp server running Ubuntu 6.06 with 1 250 GB IDE drive (10 GB for system and 240 GB for /home which includes upload section) and 5 400 GB SATA I drives all mounted to different folders under /home/ftp. I would like to convert the 5 disks into a RAID 5 array (of course, I plan to backup all the data and reload after the array is in place).

My question is am I right in assuming that it doesn't matter how the drives are connected, say 2 on the motherboard and 3 on a (non-raid) SATA controller, or whatever, as long as Linux can access all 5 drives (sda-sde)? Thanks.

You are correct. Software RAID has almost no restrictions - you just need block devices. For example, I'm running a RAID-5 array with 4 external Firewire drives. You can mix and match IDE, SATA, USB, Firewire and it will work (though performance will be limited by the slowest drive).

Wonderful. That's what I needed to know. The rest I should be able to get from howtos.