There are third party hardware RAID controllers you can buy. Others on this board have warned agains SATA RAID controllers because often they aren't true RAID.
There is also "sofware" RAID built into Linux. Do "man mdadm" for details on that. This doesn't require a card.
/etc/init.d is where the base init scripts are typically.
/etc/rc0.d, /etc/rc1.d, /etc/rc2.d, /etc/rc3.d, /etc/rc4.d, /etc/rc5.d & /etc/rc6.d are the run level directories. The files there are links back to the files in /etc/init.d.
S##name are start links and K##name are kill (stop) links.