Re: please help - raid 1 degraded

[Adam Goryachev <mailinglists@websitemanagers.com.au>]

On 12/02/15 05:04, sunruh@prismnet.com wrote:
> centos 6.6
> 2x 240gig ssd in raid1
> this is a live running production machine and the raid1 is for /u of
> users home dirs.
>
> 1 ssd went totally offline and i replaced it after noticing the firmware
> levels are not the same.  the new ssd has the same level firmware.
>
> /dev/sdb is the good ssd
> /dev/sdc is the new blank ssd
>
> when working it was /u1 from /dev/md127p1 and /u2 from /dev/md127p2
> p1 is 80gig and p2 is 160gig for the full 240gig size of the ssd
>
>> ls -al /dev/md*
> brw-rw---- 1 root disk   9, 127 Feb 11 11:09 /dev/md127
> brw-rw---- 1 root disk 259,   0 Feb 10 20:23 /dev/md127p1
> brw-rw---- 1 root disk 259,   1 Feb 10 20:23 /dev/md127p2
>
> /dev/md:
> total 8
> drwxr-xr-x  2 root root  140 Feb 10 20:24 .
> drwxr-xr-x 20 root root 3980 Feb 10 20:24 ..
> lrwxrwxrwx  1 root root    8 Feb 11 11:09 240ssd_0 -> ../md127
> lrwxrwxrwx  1 root root   10 Feb 10 20:23 240ssd_0p1 -> ../md127p1
> lrwxrwxrwx  1 root root   10 Feb 10 20:23 240ssd_0p2 -> ../md127p2
> -rw-r--r--  1 root root    5 Feb 10 20:24 autorebuild.pid
> -rw-------  1 root root   63 Feb 10 20:23 md-device-map
>
>> ps -eaf | grep mdadm
> root      2188     1  0 Feb10 ?        00:00:00 mdadm --monitor --scan -f --pid-file=/var/run/mdadm/mdadm.pid
>
> how do i rebuild /dev/sdc into the mirror of /dev/sdb?
>

Please send the output of fdisk -lu /dev/sd[bc] and cat /proc/mdstat 
(preferably both when it was working and current).

In general, when replacing a failed RAID1 disk, and assuming you 
configured it the way I think you did:
1) fdisk -lu /dev/sdb
Find out the exact partition sizes
2) fdisk /dev/sdc
Create the new partitions exactly the same as /dev/sdb
3) mdadm --manage /dev/md127 --add /dev/sdb1
Add the partition to the array
4) cat /proc/mdstat
Watch the rebuild progress, once it is complete, relax.

PS, steps 1 and 2 may not be needed if you are using the full block 
device instead of a partition. Also, change the command in step 3 to 
"mdadm --manage /dev/md127 --add /dev/sdb"

PPS, if this is a bootable disk, you will probably also need to do 
something with your boot manager to get that installed onto the new disk 
as well.

Hope this helps, otherwise, please provide more information.


Regards,
Adam

-- 
Adam Goryachev Website Managers www.websitemanagers.com.au