Re: mdadm ignoring X as it reports Y as failed

[NeilBrown <neilb@suse.de>]

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On Sat, 06 Jul 2013 21:06:14 +0200 "Marek Jaros" <mjaros1@nbox.cz> wrote:

> Hey everybody.
> 
> To keep it short, I have a RAID-5 mdraid, just today 2 out of the 5  
> drives dropped out. It was a cable issue and has since been fixed. The  
> array was not being written to or utilized in other way so no data has  
> been lost.
> 
> However when I attempted to reassemble the array with
> 
> mdadm --assemble --force --verbose /dev/md0 /dev/sdc /dev/sdd /dev/sde  
> /dev/sdf /dev/sdg
> 
> 
> I got the folowing errors
> 
> mdadm: looking for devices for /dev/md0
> mdadm: /dev/sdc is identified as a member of /dev/md0, slot 0.
> mdadm: /dev/sdd is identified as a member of /dev/md0, slot 1.
> mdadm: /dev/sde is identified as a member of /dev/md0, slot 2.
> mdadm: /dev/sdf is identified as a member of /dev/md0, slot 3.
> mdadm: /dev/sdg is identified as a member of /dev/md0, slot 4.
> mdadm: ignoring /dev/sde as it reports /dev/sdc as failed
> mdadm: ignoring /dev/sdf as it reports /dev/sdc as failed
> mdadm: ignoring /dev/sdg as it reports /dev/sdc as failed
> mdadm: added /dev/sdd to /dev/md0 as 1
> mdadm: no uptodate device for slot 2 of /dev/md0
> mdadm: no uptodate device for slot 3 of /dev/md0
> mdadm: no uptodate device for slot 4 of /dev/md0
> mdadm: added /dev/sdc to /dev/md0 as 0
> mdadm: /dev/md0 assembled from 2 drives - not enough to start the array.
> 

Try the same assemble command, but rearrange the devices so that one of sde
sdf sdg is first.  That might work.

The super blocks all have the same event count, but report different things
about which devices have failed.  That shouldn't really happen but it
obviously did.
I'll see if I can figure out how to make mdadm cope correctly with this
situation.

Thanks for the report,

NeilBrown


> 
> After doing --examine* I indeed found out that the StateArray info  
> inside the superblock has marked the first two drives as missing. That  
> is however not true anymore but I can't force it to assemble the array  
> or update the superblock info.
> 
> So is there anyway to force mdadm to assemble the array? Or perhaps  
> edit the superblock info manually? I'd rather avoid having to recreate  
> the array from scratch.
> 
> Any help or pointers with more info are highly appreciated. Thank you.
> 
> 
> Regards,
> 
> Marek Jaros
> 
> 
> *--examine output here:
> 
> /dev/sdc:
>            Magic : a92b4efc
>          Version : 1.2
>      Feature Map : 0x0
>       Array UUID : 43222604:a15a957d:313d7b6c:d087ba6a
>             Name : YSGARD:0
>    Creation Time : Thu Apr 25 12:38:17 2013
>       Raid Level : raid5
>     Raid Devices : 5
> 
>   Avail Dev Size : 1953263024 (931.39 GiB 1000.07 GB)
>       Array Size : 3906525184 (3725.55 GiB 4000.28 GB)
>    Used Dev Size : 1953262592 (931.39 GiB 1000.07 GB)
>      Data Offset : 262144 sectors
>     Super Offset : 8 sectors
>            State : clean
>      Device UUID : d2a4d8ed:b2c2bf12:6d553d16:7aabe804
> 
>      Update Time : Sat Jul  6 14:43:14 2013
>         Checksum : 1b569235 - correct
>           Events : 2742
> 
>           Layout : left-symmetric
>       Chunk Size : 512K
> 
>     Device Role : Active device 0
>     Array State : AAAAA ('A' == active, '.' == missing)
> /dev/sdd:
>            Magic : a92b4efc
>          Version : 1.2
>      Feature Map : 0x0
>       Array UUID : 43222604:a15a957d:313d7b6c:d087ba6a
>             Name : YSGARD:0
>    Creation Time : Thu Apr 25 12:38:17 2013
>       Raid Level : raid5
>     Raid Devices : 5
> 
>   Avail Dev Size : 1953263024 (931.39 GiB 1000.07 GB)
>       Array Size : 3906525184 (3725.55 GiB 4000.28 GB)
>    Used Dev Size : 1953262592 (931.39 GiB 1000.07 GB)
>      Data Offset : 262144 sectors
>     Super Offset : 8 sectors
>            State : clean
>      Device UUID : f729ddca:adb2eaec:748ad0b6:0e321903
> 
>      Update Time : Sat Jul  6 14:29:42 2013
>         Checksum : 7149bfc6 - correct
>           Events : 2742
> 
>           Layout : left-symmetric
>       Chunk Size : 512K
> 
>     Device Role : Active device 1
>     Array State : AAAAA ('A' == active, '.' == missing)
> /dev/sde:
>            Magic : a92b4efc
>          Version : 1.2
>      Feature Map : 0x0
>       Array UUID : 43222604:a15a957d:313d7b6c:d087ba6a
>             Name : YSGARD:0
>    Creation Time : Thu Apr 25 12:38:17 2013
>       Raid Level : raid5
>     Raid Devices : 5
> 
>   Avail Dev Size : 1953263024 (931.39 GiB 1000.07 GB)
>       Array Size : 3906525184 (3725.55 GiB 4000.28 GB)
>    Used Dev Size : 1953262592 (931.39 GiB 1000.07 GB)
>      Data Offset : 262144 sectors
>     Super Offset : 8 sectors
>            State : clean
>      Device UUID : 83aea2f7:dc6a7d68:0d875248:c54d2bc9
> 
>      Update Time : Sat Jul  6 14:46:15 2013
>         Checksum : 713418b2 - correct
>           Events : 2742
> 
>           Layout : left-symmetric
>       Chunk Size : 512K
> 
>     Device Role : Active device 2
>     Array State : ..AAA ('A' == active, '.' == missing)
> /dev/sdg:
>            Magic : a92b4efc
>          Version : 1.2
>      Feature Map : 0x0
>       Array UUID : 43222604:a15a957d:313d7b6c:d087ba6a
>             Name : YSGARD:0
>    Creation Time : Thu Apr 25 12:38:17 2013
>       Raid Level : raid5
>     Raid Devices : 5
> 
>   Avail Dev Size : 1953263024 (931.39 GiB 1000.07 GB)
>       Array Size : 3906525184 (3725.55 GiB 4000.28 GB)
>    Used Dev Size : 1953262592 (931.39 GiB 1000.07 GB)
>      Data Offset : 262144 sectors
>     Super Offset : 8 sectors
>            State : clean
>      Device UUID : b8295773:a4a73e18:6a097100:15ecc829
> 
>      Update Time : Sat Jul  6 14:46:15 2013
>         Checksum : b565f15d - correct
>           Events : 2742
> 
>           Layout : left-symmetric
>       Chunk Size : 512K
> 
>     Device Role : Active device 4
>     Array State : ..AAA ('A' == active, '.' == missing)
> 
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