Recovering/Restoring Boot Partition

[Chris Murphy]

On Feb 22, 2014, at 12:46 PM, Don Levey <fedora-list at the-leveys.us> wrote:

> On 2/21/2014 11:38, Chris Murphy wrote:
>> 
>> On Feb 21, 2014, at 5:29 AM, Don Levey <fedora-list at the-leveys.us>
>> wrote:
>>>> No. Hardware raid will show up as a single /dev/sdX device. What 
>>>> results do you get for lsblk?
>> 
>> It's a nitpick, but for what it's worth it's always best to include
>> the command used. I understand the motivation to keep things tidy,
>> and concise, but in this case we're talking about one additional
>> line.
>>>> 
>>>> 
>>> NAME                   MAJ:MIN RM   SIZE RO TYPE MOUNTPOINT sda
>>> 8:0    0   149G  0 disk &#9492;&#9472;sda3     		  8:3    0  99.8G
>>> 0 part &#9500;&#9472;vg_dauphin-lv_root 253:0    0  94.9G  0 lvm
>>> / &#9492;&#9472;vg_dauphin-lv_swap 253:1    0     5G  0 lvm
>>> [SWAP] sdb                    		  8:16   1   7.6G  0 disk 
>>> &#9492;&#9472;sdb1    		  8:17   1   7.6G  0 part sdc
>>> 8:32   0   149G  0 disk &#9500;&#9472;sdc1     		  8:33   0    49G
>>> 0 part &#9500;&#9472;sdc2     		  8:34   0   200M  0 part 
>>> &#9492;&#9472;sdc3      	  8:35   0  99.8G  0 part
>> [snipped all loop and live devices]
>> 
>> Are you certain this is hardware raid and not
>> firmware/BIOS/motherboard raid?  What is the make/model of hardware
>> raid card? Did you choose one disk or two disks, in the Fedora
>> installer?
>> 
> It is likely motherboard RAID; in my ignorance I thought they were the
> same thing.  When installing, I chose 1 disk, if I recall correctly (it
> was a while ago).
> 
>> It looks to me like sda and sdc have the same partitions and sizes,
>> and suggests they should be in a raid1 configuration. I think sdb is
>> probably USB flash media of the Fedora installer.
>> 
>> What it looks like to me is that this is actually IMSM RAID, which is
>> a firmware initiated RAID but then is software raid after that. And
>> for whatever reason it's not being properly initiated. The fact the
>> first partition starts at LBA 63 suggests Windows XP at least
>> originally.
>> 
> It has been dual boot, with XP and Fedora.  The XP partition seems to
> still work without issue.
> 
>> What do you get for:
>> 
>> mdadm -E /dev/sda mdadm -E /dev/sdc
>> 
>> 
> (this time, with commands, because I can learn. :-) )
> 
> [root at localhost don]# mdadm -E /dev/sda
> /dev/sda:
>   MBR Magic : aa55
> Partition[0] :    102760449 sectors at           63 (type 07)
> Partition[1] :       409600 sectors at    102760512 (type 83)
> Partition[2] :    209326268 sectors at    103170112 (type 8e)
> [root at localhost don]# mdadm -E /dev/sdc
> /dev/sdc:
>   MBR Magic : aa55
> Partition[0] :    102760449 sectors at           63 (type 07)
> Partition[1] :       409600 sectors at    102760512 (type 83)
> Partition[2] :    209326268 sectors at    103170112 (type 8e)
> 
> So yes, they seem to be relating the same thing.

It's not finding the IMSM metadata if this is firmware raid. In the BIOS setup, you should find some setting related to this. Typically the option setting is either raid, ide, or ahci. Maybe it was set to raid when you initially did the install and then got changed to ide? I wouldn't change it from what it is now, but it's worth checking the setting to see if you recall it being changed recently.

Also show the result from each:

cat /proc/mdstat
pvck /dev/sda3
pvck /dev/sdc3

What I'm betting on at this point (guessing), is that the raid array is not active, and therefore two identical UUID physical volumes are present rather than appearing as one, and grub is becoming confused.

And the other problem is that there simply isn't enough space to embed core.img in the MBR gap as usual, because the support modules for RAID and LVM make it too big. There is a way to use block lists, but before doing that the whole raid thing needs to be figured out.

I haven't done a lot of testing in this area with actual hardware but some people say using software raid between Windows and Linux is flakey. I think it ought to work or it's a bug. But the thing to realize is that you have a Windows driver doing software raid when Windows is running; and then you have a linux driver doing software raid when linux is running. So it's absolutely got to work correctly or you've totally defeated the purpose of even having raid1, and instead you're better off with just a regular consistent backup, like once an hour or something.



Chris Murphy