Re: Disc failure on a software RAID system has killed everything

On 05/19/2010 12:04 PM, Gary Stainburn wrote:
Hi folks,

I've got a PC with 5x500GB HDD's running software raid. On drive 0 and 1 I
had RAID0 for the boot partition and then on all 5 drives I had RAID 5 for
everything else.

Why use RAID0 for the boot partition? That means that a failure of
either drive will make the system unbootable (since half the file system
needed for booting is on the dead device).

I tend to use RAID1 for boot devices, RAID5 for general storage (where I
either don't care too much about write performance or expect a low level
of write I/O). I would only use RAID0 for transient data that can be
easily regenerated after a hardware failure (or combine it with RAID1 if
you need to combine redundancy with better write performance but make
sure you understand the way that different stackings behave[1]).

One of the first two drives has died causing the PC to hang, and then when I
rebooted it couldn't get past GRUB. I have found out which drive it is and
disconnected it. It then got past GRUB, loaded the kernel which then paniced
and hung.

If the boot file system was really stored on a RAID0 device one side of
which is now absent then it is possible that we are loading a broken
vmlinuz or initrd (initramfs) image from the surviving disk.

I have tried booting using a FC11 install DVD (I believe the dead PC is either
FC9 or FC10) and going into rescue mode but it says that there are no Linux
partitions and doesn't go any further.

You might need to activate the arrays manually depending on how they
were configured.

Going into fdisk for each drive (with the dead one still disconnected) shows
the partition tables.

in theory, this system should still be bootable, can anyone suggest things to
try to get it working again.

I'm not sure I agree if you had /boot on a RAID0.

Regards,
Bryn.
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