[CentOS] raid 1

[CentOS List]

> CentOS List wrote:
>>> CentOS List wrote:
>>>>>>>> I am running raid 1 on a centos 4.4. One of the harddisk (sda1) 
>>>>>>>> failed. How can i carry on running the server using only sda2?
>>>>>>>
>>>>>>> Generate a grub floppy and use that to load the grub menu from the 
>>>>>>> sdb (probably now sda) disk.
>>>>>>>
>>>>>>> If you are really talking about sda1 and sda2, those are partitions 
>>>>>>> on the same disk.
>>>>>>
>>>>>> Is there a detail step by step howto? The raid 1 has no LVM. just 
>>>>>> md0, md1 and md2. md0 is /boot, md1 is swap and md2 is the storage. I 
>>>>>> had replace sba with a new disk. I tried to boot up and it says 
>>>>>> kernel panic. How am i going to reconstruct the raid and sync sdb to 
>>>>>> sda?
>>>>>
>>>>> It might be easier to swap the old sdb into the sda position so you'll 
>>>>> boot from it, but you should also be able to boot the install cd with
>>>>
>>>> If swapped and booted, and got a kernel panic error.
>>>
>>>>> 'linux rescue' at the boot prompt, let it detect and mount your system 
>>>>> (which will be the 'broken' raid devices with their single members),
>>>>
>>>> If i use linux rescue, The 3 mds I created are gone. /cat /proc/mdstat 
>>>> says Personalitlies: [raid0] [raid1] [raid5] [raid6], no longer 
>>>> Personalities : [raid1]
>>>
>>> Perhaps your raid wasn't really working the way you thought before. From 
>>> the rescue boot, does fdisk show the 3 partitions on the old disk with 
>>> type 'fd'?  Can you mount the old /boot and / partitions somewhere by 
>>> hand?  You should be able to do this with the /dev/sda1 and /dev/sda3 
>>> device names if the md devices aren't detected at boot.
>>
>> cat /proc/partitions still shows me the 3 partitions.
>
> Does fdisk say that they are type 'fd'(raid autodetect)?
>
>> I actually copied /boot to the "replaced disk" and it is able to boot up, 
>> but without any filesystem, so i guess the boot is still intact. So do i 
>> need to mount /boot and /?
>
> If you can get the original partitions to be detected as their md devices 
> you should fdisk matching partitions on the replacement disk, then 
> 'mdadm --add ...' to add them and they will automatically sync up.

mdadm --create --verbose /dev/md0 --level=1 --raid-devices=2 /dev/sda1 
/dev/sdb1
mdadm --create --verbose /dev/md1 --level=1 --raid-devices=2 /dev/sda2 
/dev/sdb2
mdadm --create --verbose /dev/md2 --level=1 --raid-devices=2 /dev/sda3 
/dev/sdb3

After that i reboot and got the kernel panic again.

md: considering sdb1
md: adding sdb1
md: created md0
md: bind<sda1>
md: running: <sdb1><sda1>
raid1: raid set md0 active with 2 out of 2 mirrors
md: ... autorun DONE
md: autodetcting RAID arrays
md:mautorun ...
Creating root device
Mounting root filesystem
switching to new root
switchroot: mount failed: 22
umount /unitrd/dev failed: 2
Kernel panic