Rescue software RAID system

[teddy]

1. Boot the working drive to confirm it works.
    Was grub enabled on both drives ?
    A lot forget this step when making a raid1.

2. Power down and drop in a new drive

3. fdisk and mdadm it and get the raid in sync.

Teddy



William Muriithi wrote:
>  > > So I booted from a rescue CD, used mdadmin to start RAID device,
> mounted the
>  > > device and tried to chroot into the mount directory and don't work,
> don't
>  > > seem to have chroot binary in my rescue environment.
>  >
>  > If this is the centos rescue environment, it definitely should include
>  > chroot. The approach you're taking seems fine to me. I've done this in
>  > the past.
>
> This eventually worked. I have now been able to bring up one of the RAID
> device up fully. This is md0 which is RAID1. I have struggled with md2
> though which is a RAID5 device. Here is how it looks.
>
> mdadm --query --detail /dev/md2
>
> /dev/md2: Version : 1.2 Creation Time : Thu Dec 13 11:04:35 2012 Raid
> Level : raid5 Used Dev Size : -1 Raid Devices : 3 Total Devices : 2
> Persistence : Superblock is persistent
>
> Update Time : Thu Nov 21 09:20:07 2013 State : active, degraded, Not
> Started Active Devices : 2 Working Devices : 2 Failed Devices : 0 Spare
> Devices : 0
>
> Layout : left-symmetric Chunk Size : 512K
>
> Name : gfs1.jamar.com:2 <http://gfs1.jamar.com:2> (local to host
> gfs1.jamar.com <http://gfs1.jamar.com>) UUID :
> 0202547e:d9a3bd67:fdeaf168: a780aa38 Events : 6292
>
> Number Major Minor RaidDevice State 0 0 0 0 removed 1 8 18 1 active sync
> /dev/sdb2 3 8 34 2 active sync /dev/sdc2
>
> mdadm --add /dev/md2 /dev/sda2 mdadm: add new device failed for
> /dev/sda2 as 4: Invalid argument
>
> On dmesg, I see the error
>
> MD2: ADD_NEW_DISK not supported
>
> (The above actually worked for the RAID 1 device on the same system. It
> has two partition, RAID 1 being system and RAID 5 being data partition).
>
> mdadm --examine /dev/sd[abc]2 | egrep 'dev|Update|Role|State|Chunk Size'
> /dev/sda2: State : active Update Time : Thu Nov 21 09:20:07 2013 Device
> Role : spare Array State : AAA ('A' == active, '.' == missing)
> /dev/sdb2: State : active Update Time : Thu Nov 21 09:20:07 2013 Device
> Role : Active device 1 Array State : AAA ('A' == active, '.' == missing)
> /dev/sdc2: State : active Update Time : Thu Nov 21 09:20:07 2013 Device
> Role : Active device 2 Array State : AAA ('A' == active, '.' == missing)
>
> What does "used device size" mean when the number is negative?
>
> Anybody see something I may have approached wrongly? Its a back up
> system so not too worried for now. Plan to just destroy the device and
> create a new if I can't bring it up by end week. Would be satisfying
> though to bring it back though
>
> William
>  >
>  > Also, in the unfortunate event that you have problems during the
>  > rebuild, be aware that unless the first failed disk is completely
>  > fubared, you may be able to use some of its data if required.
>  > Hopefully not, but keep it in mind.
>  >
>  > Thanks
>  > -Ben
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