Re: mdadm and fsck

[Joey L <mjh2000@gmail.com>]

Thanks for the scripts and the reply !! now i think i understand raid on linux a lot better - but do have additional questions :)

My /dev/md0 the root filesystem came back - Thank God !! and you :)

Info you requested :

root@rider:~# mdadm --detail /dev/md0

/dev/md0:

        Version : 1.2

  Creation Time : Mon Jun 27 08:51:23 2011

     Raid Level : raid1

     Array Size : 972654456 (927.60 GiB 996.00 GB)

  Used Dev Size : 972654456 (927.60 GiB 996.00 GB)

   Raid Devices : 2

  Total Devices : 2

    Persistence : Superblock is persistent

    Update Time : Sat Sep 17 22:53:59 2011

          State : clean

 Active Devices : 2

Working Devices : 2

 Failed Devices : 0

  Spare Devices : 0

           Name : debian:0

           UUID : f696d568:1f4226e3:42f0a70a:68e284a7

         Events : 295206

    Number   Major   Minor   RaidDevice State

       2       8        1        0      active sync   /dev/sda1

       1       8       17        1      active sync   /dev/sdb1

-- this looks fine !

But my issue is /dev/md1 -- i rebooted the machine - now it does not come up at all and do not know which drive i think is okay - I see both in fdisk -l  and they are okay.

I get this:

root@rider:~# mdadm --detail /dev/md1

mdadm: cannot open /dev/md1: No such file or directory

root@rider:~# fdisk -l /dev/sdc

Disk /dev/sdc: 1000.2 GB, 1000204886016 bytes

255 heads, 63 sectors/track, 121601 cylinders

Units = cylinders of 16065 * 512 = 8225280 bytes

Sector size (logical/physical): 512 bytes / 512 bytes

I/O size (minimum/optimal): 512 bytes / 512 bytes

Disk identifier: 0x000d27a0

   Device Boot      Start         End      Blocks   Id  System

/dev/sdc1               1      121601   976760001   fd  Linux raid autodetect

root@rider:~# fdisk -l /dev/sdc1

Disk /dev/sdc1: 1000.2 GB, 1000202241024 bytes

255 heads, 63 sectors/track, 121600 cylinders

Units = cylinders of 16065 * 512 = 8225280 bytes

Sector size (logical/physical): 512 bytes / 512 bytes

I/O size (minimum/optimal): 512 bytes / 512 bytes

Disk identifier: 0x00000000

     Device Boot      Start         End      Blocks   Id  System

root@rider:~# fdisk -l /dev/sdd

Disk /dev/sdd: 1000.2 GB, 1000204886016 bytes

255 heads, 63 sectors/track, 121601 cylinders

Units = cylinders of 16065 * 512 = 8225280 bytes

Sector size (logical/physical): 512 bytes / 512 bytes

I/O size (minimum/optimal): 512 bytes / 512 bytes

Disk identifier: 0x000d4cc8

   Device Boot      Start         End      Blocks   Id  System

/dev/sdd1               1      121601   976760001   fd  Linux raid autodetect

root@rider:~# fdisk -l /dev/sdd1

Disk /dev/sdd1: 1000.2 GB, 1000202241024 bytes

255 heads, 63 sectors/track, 121600 cylinders

Units = cylinders of 16065 * 512 = 8225280 bytes

Sector size (logical/physical): 512 bytes / 512 bytes

I/O size (minimum/optimal): 512 bytes / 512 bytes

Disk identifier: 0x00000000

Disk /dev/sdd1 doesn't contain a valid partition table

How do I determine which drive is the key drive or the one to add first to /dev/md1

thanks

mjh

On Sat, Sep 17, 2011 at 12:23 PM, Andrew McGlashan <andrew.mcglashan@affinityvision.com.au> wrote:

Hi,

Joey L wrote:

I have a broken raid1 drive set - i was able to fix 1 but the other raid still has issues.

You fixed the file system with fsck.  One drive [of md0] is considered fine, the other is becoming fine during the rebuild.

i have gone through the tutorials online to bring it back online but still unable to bring it back.

Do i have to run fsck on the individual member drives ???

No.

my /proc/mdstat looks like:
Personalities : [raid1]
md1 : active raid1 sdc1[0] sdd1[1](S)
     976758841 blocks super 1.2 [2/1] [U_]

Not sure, but it _may_ be that md1 will rebuild itself using the "*S*pare" when md0 is fully rebuilt.

md0 : active raid1 sda1[2] sdb1[1]
     972654456 blocks super 1.2 [2/1] [_U]
     [==========>..........]  recovery = 50.7% (493690944/972654456) finish=416.5min speed=19162K/sec

..

my questions is :
1. how can i bring it back online.

If one RAID1 member is fine, then the file system should be accessible.  It will just operate in degraded mode in the meantime.

2. what is the (S) mean ?

This is a hot spare, not sure why it isn't rebuilding now....  whilst md0 is rebuilding.

3. how do i run fsck or other utility on ext4 filesystem ?

You only run fsck to fix a file system, not to fix a RAID set.  If the file system won't mount, then you could try fsck on the md0 or md1 device as required _before_ you mount it

4. do i run it on the raid1 device /dev/md0 or on the individual devices /dev/sda and /devsdb

You would run fsck on the md0 device in your case, but that is your root file system -- is it mounted now?  If it is, then no fsck....

Your md1 seems to have been your swap partition, swap doesn't have any file system on it to fsck.  But it is now /mnt/raid ????

It might be useful for to supply output from blkid if you need more help.  And also output from the following:
 mdadm --detail /dev/md0
 mdadm --detail /dev/md1

That [mdadm --detail .... ] will give more details than /proc/mdstat


--
Kind Regards
AndrewM

Andrew McGlashan