Help needed - RAID5 recovery from Power-fail - without HTML

[Nigel J. Terry]

Guys

Thanks for the prompt responses. Sorry I have only just got back to
this. The powerfail was a result of moving house and my wife thinks that
unpacking and putting up shelves is more important than my server...

I have investigated some more. This array of 2 * 250GB disks was set up
as RAID5 with the aim of adding another drive later. I have bought that
drive today, but not yet installed it. In the 2 disk state it appears to
give 250GB of storage. I can provide the following extra information:

# cat /proc/mdstat
Personalities : [raid5]
unused devices: <none>

# mdadm --query /dev/md0
/dev/md0: is an md device which is not active

# mdadm --query /dev/md0
/dev/md0: is an md device which is not active
/dev/md0: is too small to be an md component.

# mdadm --query /dev/sda1
/dev/sda1: is not an md array
/dev/sda1: device 0 in 2 device undetected raid5 md0.  Use mdadm
--examine for more detail.

#mdadm --query /dev/sdb1
/dev/sdb1: is not an md array
/dev/sdb1: device 1 in 2 device undetected raid5 md0.  Use mdadm
--examine for more detail.

# mdadm --examine /dev/md0
mdadm: /dev/md0 is too small for md

# mdadm --examine /dev/sda1
/dev/sda1:
          Magic : a92b4efc
        Version : 00.90.02
           UUID : c57d50aa:1b3bcabd:ab04d342:6049b3f1
  Creation Time : Thu Dec 15 15:29:36 2005
     Raid Level : raid5
   Raid Devices : 2
  Total Devices : 2
Preferred Minor : 0

    Update Time : Tue Mar 21 06:25:52 2006
          State : active
 Active Devices : 1
Working Devices : 1
 Failed Devices : 2
  Spare Devices : 0
       Checksum : 2ba99f09 - correct
         Events : 0.1498318

         Layout : left-symmetric
     Chunk Size : 128K

      Number   Major   Minor   RaidDevice State
this     0       8        1        0      active sync   /dev/sda1

   0     0       8        1        0      active sync   /dev/sda1
   1     1       0        0        1      faulty removed

#mdadm --examine /dev/sdb1
/dev/sdb1:
          Magic : a92b4efc
        Version : 00.90.02
           UUID : c57d50aa:1b3bcabd:ab04d342:6049b3f1
  Creation Time : Thu Dec 15 15:29:36 2005
     Raid Level : raid5
   Raid Devices : 2
  Total Devices : 2
Preferred Minor : 0

    Update Time : Tue Mar 21 06:23:57 2006
          State : active
 Active Devices : 2
Working Devices : 2
 Failed Devices : 0
  Spare Devices : 0
       Checksum : 2ba99e95 - correct
         Events : 0.1498307

         Layout : left-symmetric
     Chunk Size : 128K

      Number   Major   Minor   RaidDevice State
this     1       8       17        1      active sync   /dev/sdb1

   0     0       8        1        0      active sync   /dev/sda1
   1     1       8       17        1      active sync   /dev/sdb1

It looks to me like there is no hardware problem, but maybe I am wrong.
I cannot find any file /etc/mdadm.conf    nor   /etc/raidtab.

How would you suggest I proceed? Thanks

Nigel

Message: 4
Date: Wed, 29 Mar 2006 13:39:57 -0600
From: Ian Pilcher <i.pilcher at comcast.net>
Subject: Re: Help needed - RAID recovery from Power-fail
To: fedora-list at redhat.com
Message-ID: <e0enqd$8cg$1 at sea.gmane.org>
Content-Type: text/plain; charset=ISO-8859-1

Nigel J. Terry wrote:

> I run FC4 (64bit).
> I have an array of two disks /dev/sda1 and /dev/sdb1 as a raid5 array
> /dev/md0 on top of which I run lvm and mount the whole lot as /home
>   

RAID-5 requires at least three disks.  The only way that a RAID-5 array
can run with two disks is in "degraded" mode -- as if the third disk had
failed.  How did you create this thing?


> md0 is not clean
> Cannot start dirty degraded array
> failed to run raid set md0
>   

That's relatively self-explanatory.  You're probably going to have to
dig up a third disk somewhere and add it to the array before it will
resync.


> fsck.ext3 No such file or directory while trying to open
> /dev/RaidGroup/RaidVolume
>   

If the RAID device can't be started, then nothing built on it "exists".


> Naturally I don't have a full backup, so somehow I need to recover if at
> all possible.
>   

Should be possible with a third disk.