RAID is a method of spreading your data across disks.
It can vary from simply treating all of your disks as one large disk (and providing no redundancy for your data) to what's known as striping where your data is written to multiple disks in a way that means if one of the disks fails, the system can still reconstruct your data from the remaining disks.
If you simply put / on one disk, tmp on another and dev on the third, this isn't RAID and doesn't provide any kind of redundancy for your data - e.g. lose disk 2 and you've lost tmp.
I think with three disks, the best option for using RAID is what's known as RAID 5 - this will make your three physical disks look like a single 'logical' disk.
All your filesystems will be put on the logical disk but the failure of a single physical disk will not result in loss of data.
Put RAID 5 into Google and you should be able to find out plenty more information - it's been a while since I had to deal with RAID so my descriptions are a little vague.
Someone else on this list will likely give a better description.
Cheers,
Ade.
> Date: Wed, 25 Jul 2007 13:11:22 -0600
> To: debian-user@lists.debian.org
> Subject: RAID vs Multiple Drives
> From: twilliams001@elp.rr.com
>
> Tell me to move this if this is the wrong place to ask, but:
>
> RAID recognizes a number of HDD's as one homogeneous drive.
>
> If I have, say, 3 HDD's, and I divide those 3 between my /, /tmp, and /dev locations (I picked arbitrary points), is that like having a virtual RAID system? Or
> not because if the /tmp goes down, it has nothing to rebuild on?
>
> TW