On Sun, 2008-11-30 at 14:49 +0100, Hans de Goede wrote: > Jeremy Katz wrote: > > On Wed, 2008-11-26 at 12:06 +0100, Hans de Goede wrote: > >> This patch removes a special case when /boot (or / without a separate /boot) is > >> on mdraid. For some reason we only allow installing grub to the mdX device then > >> instead of allowing both the mbr of the 1st disk and the device holding /boot. > >> > >> I've searched through the anaconda history and this special handling of mdraid > >> /boot has been there since before Feb. 2002, it was inherited from before booty > >> was introduced and it does not seem to make sense. Either we cannot have /boot > >> on mdraid at all (in all cases except for raid1) or we can have /boot on dmraid > >> (in case of raid1) and then it does not matter if the bootstrap of grub starts > >> on the mbr or on the first sector of a partition. > > > > The reason we install to the mdX device is so that if your disk dies, > > the bootloader install is mirrored[1] to both disks. So while it is > > technically possible to install to the mbr of the first disk, doing so > > loses the redundancy of the RAID install. > > Well, that is pretty useless, this could be usefull when the first disk (as > seen by the BIOS) dies, except that if 99% of the cases that happens the BIOS > will still see the disk and thus still try to boot from it and fail. Some BIOSes actually fail over gracefully from this to the second disk -- shocking that a BIOS would do something useful, but it occasionally happens :-). But even in the cases of not, pulling the disk and being able to boot is something that customers have actually counted on. > Software raid1 really only protects against data loss and keeps the system > running when a disk dies. It does not guarantee the system will still (re)boot > if a disk dies. > > Moreover, grub (booty) does not actually install to the mdX device, it will > only install to the first partition of the raid set. Atleast that is how I read > the booty code. And this is no surprise as grub does not know anything about > mdraid. grub doesn't know anything about it, but the code should be there to install to both sides of the array. It's a bit fugly and nowhere as nice as LILO where this just worked thanks to dledford's work. But it should be functional at least since, iirc, FC6 times Jeremy _______________________________________________ Anaconda-devel-list mailing list Anaconda-devel-list@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/anaconda-devel-list
