I've just set up my Linux boot device as a RAID-1. Seems to work OK. I've not been sure about what to do with swap space. Googling turned up this interesting statement http://tldp.org/HOWTO/Software-RAID-HOWTO-2.html
There's no reason to use RAID for swap performance reasons. The kernel itself can stripe swapping on several devices, if you just give them the same priority in the /etc/fstab file.
A nice /etc/fstab looks like:
/dev/sda2 swap swap defaults,pri=1 0 0
/dev/sdb2 swap swap defaults,pri=1 0 0
/dev/sdg2 swap swap defaults,pri=1 0 0
This setup lets the machine swap in parallel on seven SCSI devices. No need for RAID, since this has been a kernel feature for a long time.
Sounds like I don't need my swap partitions inside a RAID. But then in the very next paragraph he says,
Another reason to use RAID for swap is high availability. If you set up a system to boot on eg. a RAID-1 device, the system should be able to survive a disk crash. But if the system has been swapping on the now faulty device, you will for sure be going down. Swapping on a RAID-1 device would solve this problem.
Is this contradicting he immediate preceding statement or am I just not reading something right? Which way is he recommending? Are non-RAID swap partitions a good thing or a bad thing?