Re: Raid 5 Problem

Michal Soltys wrote:

nterry wrote:

quoted

Hi.  I hope someone can tell me what I have done wrong.  I have a 4 
disk Raid 5 array running on Fedora9.  I've run this array for 2.5 
years with no issues.  I recently rebooted after upgrading to Kernel 
2.6.27.7.  When I did this I found that only 3 of my disks were in 
the array.  When I examine the three active elements of the array 
(/dev/sdd1, /dev/sde1, /dev/sdc1) they all show that the array has 3 
drives and one missing.  When I examine the missing drive it shows 
that all members of the array are present, which I don't understand! 
When I try to add the missing drive back is says the device is busy.  
Please see below and let me know what I need to do to get this 
working again.  Thanks Nigel:

==================================================================
[root@homepc ~]# cat /proc/mdstat
Personalities : [raid6] [raid5] [raid4]
md0 : active raid5 sdd1[0] sdc1[3] sde1[1]
     735334656 blocks level 5, 128k chunk, algorithm 2 [4/3] [UU_U]
    md_d0 : inactive sdb[2](S)
     245117312 blocks
     unused devices: <none>
[root@homepc ~]#

For some reason, it looks like you have 2 raid arrays visible - md0 
and md_d0. The latter took sdb (not sdb1) as its component.

sd{c,d,e}1 is in assembeld array (with appropriately updated 
superblocks), thus mdadm --examine calls show one device as removed, 
but sdb is part of another inactive array, and the superblock is 
untouched and shows "old" situation. Note that 0.9 superblock is 
stored at the end  of the device (see md(4) for details), so its 
position could be valid for both sdb and sdb1.

This might be an effect of --incremental assembly mode. Hard to tell 
more without seeing startup scripts, mdadm.conf, udev rules, partition 
layout... Did upgrade involve anything more besides kernel ?

Stop both arrays, check mdadm.conf, assemble md0 manually (mdadm -A 
/dev/md0 /dev/sd{c,d,e}1 ), verify situation with mdadm -D. If 
everything looks sane, add /dev/sdb1 to the array. Still, w/o checking 
out startup stuff, it might happen again after reboot. Adding DEVICE 
/dev/sd[bcde]1 to mdadm.conf might help though.

Wait a bit for other suggestions as well.

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I don't think the Kernel upgrade actually caused the problem.  I tried 
booting up on an older (2.6.27.5) kernel and that made no difference.  I 
checked the logs for anything else that might have made a difference, 
but couldn't see anything that made any sense to me.  I did note that on 
an earlier update mdadm was upgraded:
Nov 26 17:08:32 Updated: mdadm-2.6.7.1-1.fc9.x86_64
and I did not reboot after that upgrade

I included my mdadm.conf with the last email and it includes ARRAY 
/dev/md0 level=raid5 num-devices=4 
devices=/dev/sdb1,/dev/sdc1,/dev/sdd1,/dev/sde1
My configuration is just vanilla Fedora9 with the mdadm.conf I sent

I've never had a /dev/md_d0 array, so that must have been automatically 
created.  I may have had other devices and partitions in /dev/md0 as I 
know I had several attempts at getting it working 2.5 years ago, and I 
had other issues when Fedora changed device naming, I think at FC7.  
There is only one partition on /dev/sdb, see below:

(parted) select /dev/sdb                                                 
Using /dev/sdb
(parted) print                                                           
Model: ATA Maxtor 6L250R0 (scsi)
Disk /dev/sdb: 251GB
Sector size (logical/physical): 512B/512B
Partition Table: msdos

Number  Start   End    Size   Type     File system  Flags    
 1      32.3kB  251GB  251GB  primary               boot, raid

So it looks like something is creating the /dev/md_d0 and adding 
/dev/sdb to it before /dev/md0 gets started.

So I tried:
[root@homepc ~]# mdadm --stop /dev/md_d0
mdadm: stopped /dev/md_d0
[root@homepc ~]# mdadm --add /dev/md0 /dev/sdb1
mdadm: re-added /dev/sdb1
[root@homepc ~]# cat /proc/mdstat
Personalities : [raid6] [raid5] [raid4]
md0 : active raid5 sdb1[4] sdd1[0] sdc1[3] sde1[1]
      735334656 blocks level 5, 128k chunk, algorithm 2 [4/3] [UU_U]
      [>....................]  recovery =  0.1% (299936/245111552) 
finish=81.6min speed=49989K/sec
     
unused devices: <none>
[root@homepc ~]#

Great - All working.  Then I rebooted and was back to square one with 
only 3 drives in /dev/md0 and /dev/sdb in /dev/md_d0
                                   
So I am still not understanding where /dev/md_d0 is coming from and 
although I know how to get things working after a reboot, clearly this 
is not a long term solution...