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

On Mon, Apr 02, 2012 at 12:18:50PM -0400, Lennart Sorensen wrote:
> 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.

Oh and if you want, I can put my debian source package for the git
checkout of grub up on my website.

Len Sorensen

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