10.04 desktop RAID 10 install?

[Tom H]

On Thu, Jun 24, 2010 at 1:54 AM, Goh Lip <g.lip at gmx.com> wrote:
> On 06/24/2010 01:21 PM, Tom H wrote:
>> On Wed, Jun 23, 2010 at 10:20 PM, Goh Lip<g.lip at gmx.com>  wrote:
>>> On 06/24/2010 09:46 AM, Alan McKay wrote:
>>>>> Make sure your boot is non-mdadm'd or RAID1.
>>>>
>>>> yeah, I'd read that somewhere.
>>>>
>>>> So I ahve it working.  I have a 512M RAID1 layed across all 4 disks
>>>> (though looks like mdadm only took the first 3 of them but I don't
>>>> care).  Then 2G swap part on each of the 4 disks.  Then the rest of
>>>> the 1T goes to a RAID10
>>>>
>>>> It is running and working great.  The only thing I am having trouble
>>>> with is grub.   It works mind you.  But one of the articles I'd read
>>>> said basically when doing the RAID1 approach for /boot, to make sure
>>>> the boot loader is installed on all of the disks in the RAID1.  And
>>>> damned if I know how to do that.  Been reading man pages and checking
>>>> google and still nothing.
>>>
>>> To install grub to other disks...
>>> grub-install --root-directory=/media/disk_other/ /dev/sdx
>>>
>>> Note it will *not* create grub.cfg file to the other disk.
>>
>> It's not quite as simple as that.
>>
>> I had said on the list some time ago that grub1 couldn't boot from an
>> mdadm'd /boot and that I'd never worked anywhere that did that.
>> Christopher C corrected me and he was right.
>>
>> Out of curiosity, I checked the RHEL documentation since this is what
>> we run and I found:
>> http://www.redhat.com/docs/manuals/enterprise/RHEL-5-manual/Installation_Guide-en-US/s1-grub-installing.html
>> http://www.redhat.com/docs/en-US/Red_Hat_Enterprise_Linux/5.5/html/Installation_Guide/s1-grub-installing.html
>>
>> The problem is that you have to trick grub in order to ensure that you
>> can boot from a degraded raid by installing grub onto sda and sdb with
>> both being (hd0).
>>
>> For grub1, you would run (assuming /boot is on sdX1):
>>
>> # grub
>> grub>  device (hd0) /dev/sda
>> grub>  root (hd0,0)
>> grub>  setup (hd0)
>> grub>  quit
>>
>> and
>>
>> # grub
>> grub>  device (hd0) /dev/sdb
>> grub>  root (hd0,0)
>> grub>  setup (hd0)
>> grub>  quit
>>
>> For grub2, the only equivalent procedure that I can think of is to
>> back up device.map, set (hd0) as /dev/sda in device.map, run
>> grub-install /dev/sda, set (hd0) as /dev/sdb in device.map, run
>> grub-install /dev/sdb.
>>
>
> Okay,right. I not worked with raid or lvm and I too have read somewhere
> these may pose some problems with grub. The solution I read is to
> disable lvm or raid, set grub in all disks and then enable these back,
> or like you said somewhere, have the /boot in a non-raid area. But, like
> I said, I've not used them.
>
> Alan appears to know what he needs to do with raid and if he just want a
> simple "How to install grub to other disks", well then...
>
> If this can be resolved with grub-legacy by your message on devicemap
> above, hope you can sort this out with grub2 too.
>
> Can this link help?
>
> http://grub.enbug.org/FranklinPiat/grub-mkdevicemap.manpage
>
> sudo grub-mkdevicemap --devicemap=FILE

The problem with grub-devicemap is that it will associate sda1 with
hd0 and sda2 with hd1 so, if sda1 fails the system will not boot.

Going back to my previous email, it might be better to create a
different device.map and run grub-install with
"--grub-mkdevicemap=/path/to/customdevivemap".