Russell Coker wrote:
Sorry, I'm not up to date on the newest features of LILO (it's cool that is supports SW/RAID now, btw), I stated this because of what I read on the Software-RAID-HOWTO.On Wed, 30 Jan 2002 17:54, jose@iteso.mx wrote:detected the drive, but during the part that "lilo: " is supposed to come up, nothing did. The disk kept grinding and grinding, and eventually asked for a floppy. I was hoping that the 2nd, working drive in the raid array would kick in any moment, but that didn't happen. Everything stalled right there.Lilo would have to know about your RAID setup (and of course it doesn't), that's why it's not recommended to use software RAID on the root partition.Who recommends that you don't use software RAID on the root file system?Not me (lilo maintainer and user of this), not the lilo author, not the software RAID kernel maintainer.
http://www.ibiblio.org/pub/Linux/docs/HOWTO/other-formats/html_single/Software-RAID-HOWTO.html'The latest official lilo distribution (Version 21) doesn't handle RAID devices, and thus the kernel cannot be loaded at boot-time from a RAID device. If you use this version, your |/boot| filesystem will have to reside on a non-RAID device. A way to ensure that your system boots no matter what is, to create similar |/boot| partitions on all drives in your RAID, that way the BIOS can always load data from eg. the first drive available. This requires that you do not boot with a failed disk in your system.'
It is stated there also that you can boot root RAID filesystems, but it requires some tweaking (applying some RedHat patches to lilo, installing on a spare disk, then copying the installation on the RAID fs...), which is less straightforward than having the / partition on a normal device.
Btw, while searching for the howto, I found several of them dealing with the issue:
http://www.ibiblio.org/pub/Linux/docs/HOWTO/other-formats/html_single/Root-RAID-HOWTO.html http://www.ibiblio.org/pub/Linux/docs/HOWTO/other-formats/html_single/Boot+Root+Raid+LILO.html
I'd say software RAID should be used on data partitions, and keep a backup of your root partition somewhere, so that when the disk holding it fails, you just swap in a new one and recover your root backup. When a disk holding the data partition (on sw/raid) fails I assume it'd work as advertised.If the primary disk fails and the BIOS and boot loader don't allow booting from the second disk then you just have to physically swap disks (which is much less effort than swapping disks and restoring from backup).You can't be 24x7-high-availability with software raid only, there's always some down time involved with it, or at least a higher risk of downtime than with hardware raid.Actually LinuxBIOS could solve this issue...