Re: grub-probe: "found two disks with the index 3 for RAID md2" after changing superblock 0.9 to 1.0

[NeilBrown <neilb@suse.de>]

[-- Attachment #1: Type: text/plain, Size: 3084 bytes --]

On Mon, 15 Sep 2014 17:12:52 +0000 Andy Smith <andy@strugglers.net> wrote:

> Hi Neil,
> 
> On Mon, Sep 15, 2014 at 05:00:37PM +1000, NeilBrown wrote:
> > On Mon, 15 Sep 2014 06:47:41 +0000 Andy Smith <andy@strugglers.net> wrote:
> > > The thing is, that bug report is quite old and is marked closed, and
> > > also states:
> > > 
> > >     "The problem is that 0.9x metadata block doesn't have enough
> > >     info to check it. With 1.x we have no such problem."
> > > 
> > > Of course, it *is* 1.x superblock. Did the poster actually mean to
> > > say that they have no problem with v1.1 and v1.2 (because they are
> > > located at or near the beginning of the device, not at the end)?
> > 
> > 0.90 has the problem, 1.x doesn't.
> 
> Right.
> 
> > Maybe there is an old 0.90 superblock confusing things.  It lives in a
> > different location than the others and so there is room for confusion.
> 
> I think that must be it.
> 
> >   mdadm --examine --metadata=0.90 /dev/sda3
> > 
> > which show you the 0.90 metadata if there is any.
> 
> /dev/sda3:
>           Magic : a92b4efc
>         Version : 0.90.01
>            UUID : 3905b303:ca604b72:be5949c4:ab051b7a
>   Creation Time : Sun Jun  4 08:18:58 2006
>      Raid Level : raid10
>   Used Dev Size : 309363264 (295.03 GiB 316.79 GB)
>      Array Size : 928089792 (885.10 GiB 950.36 GB)
>    Raid Devices : 6
>   Total Devices : 6
> Preferred Minor : 2
> 
>     Update Time : Sun Aug 24 14:26:50 2014
>           State : clean
>  Active Devices : 6
> Working Devices : 6
>  Failed Devices : 0
>   Spare Devices : 0
>        Checksum : e613d577 - correct
>          Events : 312149996
> 
>          Layout : near=2
>      Chunk Size : 64K
> 
>       Number   Major   Minor   RaidDevice State
> this     5       8        3        5      active sync   /dev/sda3
> 
>    0     0       8       51        0      active sync   /dev/sdd3
>    1     1       8       67        1      active sync
>    2     2       8       83        2      active sync
>    3     3       8       19        3      active sync   /dev/sdb3
>    4     4       8       35        4      active sync   /dev/sdc3
>    5     5       8        3        5      active sync   /dev/sda3
> 
> This shows the array when it had 6 devices as well, so clearly from
> before the metadata update and shrink to 4 devices.
> 
> >   mdadm --zero-super --metadata=0.90 /dev/sda3
> > 
> > will remove any 0.90 metadata.
> 
> Trying that whole the array is running:
> 
> mdadm: Couldn't open /dev/sda3 for write - not zeroing
> 
> This needs to be done with the array stopped, presumably?

It's preferred, but if you are really confident (and I think you are), then
adding --force is justified and should make it work.

NeilBrown


> 
> Thanks for the explanation!
> 
> Cheers,
> Andy
> --
> To unsubscribe from this list: send the line "unsubscribe linux-raid" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html


[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 828 bytes --]