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Re: Howto for md(raid 1) on PPC ?

On Mon, Apr 02, 2012 at 05:19:34PM +0200, Niels S. Eliasen wrote:
> Dó you have a cookbook for getting grub2 working(with the raid of course) ?

Well I can tell you what my setup is.

I am using an IBM p710 (and I also have a p520 with a very similar setup
although currently using a somewhat patched and manually installed via
dd and other hacks that you wouldn't want to know about).

I currently have:

sda1: about 8MB, type PReP boot, flagged as bootable
sda2: 1GB, type linux raid
sda3: 140GB, type linux raid

sdb and sdc are exactly the same.

sda2, sdb2 and sdc2 are raid1 (I have 3 disks and I want all of them to
be able to boot, so raid1 over 3 disks seemed fine).

sda3, sdb3 and sdc3 are in raid5 and is currently / but I will change
that to LVM when I reinstall the machine later this week.

I am using grub from git checked out 20120320.  I am also using the
3.2.0 backport kernel since it appears there is a problem with 2.6.32
and software raid.  grub-probe would often get garbage trying to read the
raid superblocks, and even using dd to read them and having them checked
by someone that knwos the format of them, they were in fact garbage,
but only sometimes.  Other times it worked.  3.2.0 on the other hand
has never returned invalid superblock data for the raid.

So using 3.2.0 backport kernel and grub compiled from git from a couple of weeks ago I can then do:

grub-install /dev/sda1

And after that, it boots fine and works as expected.  Well on the serial
console, the boot menu doesn't actually display quite right, so perhaps
that could use some work still.

For redundancy I actually do:

grub-install /dev/sdc1
grub-install /dev/sdb1
grub-install /dev/sda1

and then update the boot disk order with:

nvsetenv boot-device "/pci@80000002000000a/pci1014,0339@0/sas/disk@0 /pci@80000002000000a/pci1014,0339@0/sas/disk@10000 /pci@80000002000000a/pci1014,0339@0/sas/disk@20000"

Since grub only sets it to the device you specified, and I want fall back
to any of the 3 disks if needed.  I haven't convinced the grub developers
to allow multiple devices to be passed to grub-install at the same time.
Perhaps later I will succeed in that.

Anyhow, that works for me.

If you are not using an IBM, then of course you won't be using a PReP
partition for booting, and probably won't be using a DOS partition
table either, which would change things a bit.  grub-install does know
about a few other types of powerpc machines, so it still ought to work
in pretty much the same way.

The actual setup of the raid was done through the debian installer the
normal way, although I only thought of adding sdc2 to the raid1 later,
so I did that manually.

Len Sorensen

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