[CentOS] raid 1

[Les Mikesell]

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.

-- 
   Les Mikesell
    lesmikesell at gmail.com