once again raid5

Hi,

we still have troubles with our raid5 array. You can find the history of the fault in detail in my other postings (11.3.2005).

I will show you my attempts.

There are 4 discs (Maxtor 250GB) in a raid5-array. One disc failed and we sent it back to Maxtor. Now, the array consists of 3 discs. I tried to reassemble it,

mdadm -A --run --force /dev/md2 /dev/hdi1 /dev/hdk1 /dev/hdo1

but i got an error:

-snip-
mdadm: failed to RUN_ARRAY /dev/md2: Invalid argument -snap-

...in /var/log/messages

-snip-

Mar 31 14:29:00 server kernel: md: md2 stopped.
Mar 31 14:29:00 server kernel: md: bind<hdo1>
Mar 31 14:29:00 server kernel: md: bind<hdi1>
Mar 31 14:29:00 server kernel: md: bind<hdk1>
Mar 31 14:29:00 server kernel: raid5: device hdk1 operational as raid disk 1
Mar 31 14:29:00 server kernel: raid5: device hdo1 operational as raid disk 3
Mar 31 14:29:00 server kernel: RAID5 conf printout:
Mar 31 14:29:00 server kernel:  --- rd:4 wd:2 fd:2
Mar 31 14:29:00 server kernel:  disk 1, o:1, dev:hdk1
Mar 31 14:29:00 server kernel:  disk 3, o:1, dev:hdo1

-snap-

Amazingly, /proc/mdstat displays the md2-array !

-snip-
md2 : inactive hdk1[1] hdi1[4] hdo1[3]

      735334848 blocks

-snap-

So, md2 is there, but inactive. I tried

mdadm --detail /dev/md2

-snip-
mdadm --detail /dev/md2
/dev/md2:

        Version : 00.90.01

Creation Time : Mon Jun 14 18:43:20 2004
Raid Level : raid5
Device Size : 245111616 (233.76 GiB 250.99 GB)
Raid Devices : 4
Total Devices : 3
Preferred Minor : 2
Persistence : Superblock is persistent

Update Time : Sun Mar 6 16:40:29 2005
State : active, degraded
Active Devices : 2
Working Devices : 3
Failed Devices : 0
Spare Devices : 1

Layout : left-symmetric
Chunk Size : 64K

UUID : 72c49e3a:de37c4f8:00a6d8a2:e8fddb2c
Events : 0.60470022

Number Major Minor RaidDevice State
0 0 0 - removed
1 57 1 1 active sync /dev/hdk1
2 0 0 - removed
3 89 1 3 active sync /dev/hdo1

4 56 1 - spare /dev/hdi1
-snap-

Okay...more details..

mdadm --detail --test --brief /dev/md2

-snip-
ARRAY /dev/md2 level=raid5 num-devices=4 spares=1 UUID=72c49e3a:de37c4f8:00a6d8a2:e8fddb2c
devices=/dev/hdk1,/dev/hdo1,/dev/hdi1
-snap-

No more information :-(

Anyone can give me useful hints?

Regards
Ronny

It looks like hdi1 doesn't think it is an active part of the array. It is just a spare.
It is as-though the array was not fully synced when hdm1 (?) failed.

Looking back through previous emails, it looks like you had 2 drive fail in a raid5 array. This means you lose. :-(

Your best bet would be:

  mdadm --create /dev/md2 --level 5 -n 4 /dev/hda1 /dev/hdk1 missing  /dev/hdo1

and hope that the data you find on md2 isn't too corrupted. You might be lucky, but I'm not holding my breath - sorry.

NeilBrown

Hello,

Mhm.

hdm is since 2 weeks stable with 3 reallocated sectors...so, maybe no much data is lost.

Okay. But, isnt it better to use build instead of create? In the the manpages (printed 5.4.2004) ...i can see

-snip-
mdadm -build device ..... -raid-devices=Z devices

This usage is similar to --create. The difference is that it creates a legacy array without a superblock. With these arrays there is no difference between initially creating the array and subsequently assembling the array, except that hopefully there is useful data there in the second case. -snap-

Thank you :-) ... so, there are no problems with the superblocks?

Regards,
Ronny

Hi !

This worked AFAIS but there are troubles with the filesystems ( no superblocks ...ext3,xfs) :-(

-snip-
~# mdadm --detail /dev/md2
/dev/md2:

        Version : 00.90.01
  Creation Time : Sun Apr  3 12:34:42 2005
     Raid Level : raid5
     Array Size : 735334848 (701.27 GiB 752.98 GB)
    Device Size : 245111616 (233.76 GiB 250.99 GB)

Raid Devices : 4
Total Devices : 3
Preferred Minor : 2
Persistence : Superblock is persistent

Update Time : Sun Apr 3 12:34:42 2005
State : clean, degraded
Active Devices : 3
Working Devices : 3
Failed Devices : 0
Spare Devices : 0

Layout : left-symmetric
Chunk Size : 64K

UUID : 39e90883:c8f824d7:16732793:9ba70289
Events : 0.60470023

Number Major Minor RaidDevice State
0 56 1 0 active sync /dev/hdi1
1 57 1 1 active sync /dev/hdk1
2 0 0 - removed
3 89 1 3 active sync /dev/hdo1
-snap-

Thanks
Ronny

ps: For people which are interested in...

-snip-

server:~# mount -t ext3 /dev/mapper/raid5--volume-home /mnt/data
mount: wrong fs type, bad option, bad superblock on /dev/mapper/raid5--volume-home,
       or too many mounted file systems
       (could this be the IDE device where you in fact use
       ide-scsi so that sr0 or sda or so is needed?)

server:~# mount -t xfs /dev/mapper/raid5--volume-data  /mnt/data
mount: /dev/mapper/raid5--volume-data: can't read superblock
-snap-