On Tue, 2010-03-23 at 13:31 -0700, solarflow99 wrote:
> hehe, this whole setup sounds like err .... a recipe for disaster

Ignoring the swap part, the biggest issue with MD RAID-1 /boot is the
case where a disk fails, but it's "still alive" from the standpoint of
the the BIOS, so it still assigns it as hd(0).  So the MBR fails to
load, so GRUB never launches.  One would have to go into the BIOS and
tell it to assign BIOS disk 80h (GRUB hd(0)) as the 2nd disk.

This is one area where FRAID-1/dmraid can be a better, transparent boot
solution, because the FRAID logic for Int13h Disk Services will be
presenting the disks as a single BIOS disk 80h, hd(0) from the
standpoint of GRUB.  Of course, I don't recommend FRAID-1/dmraid for
anything but /boot on an enterprise system.

Which brings us back to considering a real (not fake) hardware RAID-1
solution, even if just a 2-disc solution** for just /boot, swap, /
(root) and select, other system volumes.  LVM Mirroring can then be
utilized for RAID-1, or MD can then be utilized for software RAID-1, 10,
5, 6, whatever, for other volumes (and even /usr, which will be largely
read-only and act like RAID-0 sans 1-2 stripes, depending if RAID 5 or
6).

-- Bryan

**A 3ware 9650SE-2LP is a low-profile, 2-channel SATA/SAS PCIe x1 slot
card that will work in just about anything, as well as "out-of-the-box"
with RHEL/Fedora (including updating any firmware -- right in the
3w-9xxx driver), solving any and all boot-time issues.  For around $150,
it buys a lot of piece-of-mind for boot/root.  ;)


-- 
Bryan J Smith       Senior Consultant       Red Hat, Inc
Professional Consulting http://www.redhat.com/consulting
mailto:[email protected]         +1 (407) 489-7013 (Mobile) 
mailto:[email protected]  (Blackberry/Red Hat-External) 
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