From mboxrd@z Thu Jan  1 00:00:00 1970
From: NeilBrown <neilb@suse.com>
Subject: Re: raid-1  starting with 1 drive after brief hiatus with cruddy controller.
Date: Mon, 19 Jun 2017 06:59:18 +1000
Message-ID: <871sqh57x5.fsf@notabene.neil.brown.name>
References: <20170618001410.6fa96469@e20>
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To: "r23@anchordrop.net" <r23@anchordrop.net>, linux-raid@vger.kernel.org
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On Sun, Jun 18 2017, r23@anchordrop.net wrote:
>
> root@mars:~/raid/bin# mdadm --misc --examine /dev/sdb2
> /dev/sdb2:
>           Magic : a92b4efc
>         Version : 1.2
>     Feature Map : 0x1
>      Array UUID : 2a3489a6:b430c744:2c89a792:98521913
>            Name : debian:0
>   Creation Time : Sat May  9 17:44:25 2015
>      Raid Level : raid1
>    Raid Devices : 2
>
>  Avail Dev Size : 9765179392 (4656.40 GiB 4999.77 GB)
>      Array Size : 4882589696 (4656.40 GiB 4999.77 GB)
>     Data Offset : 262144 sectors
>    Super Offset : 8 sectors
>    Unused Space : before=262056 sectors, after=0 sectors
>           State : clean
>     Device UUID : 4697b088:5d3b1ae5:55d30f65:516df63d
>
> Internal Bitmap : 8 sectors from superblock
>     Update Time : Wed Jun 14 23:53:27 2017
>   Bad Block Log : 512 entries available at offset 72 sectors
>        Checksum : 1f245410 - expected 1f249410

^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

checksum is wrong.

> root@mars:~/raid/bin/util/lsdrv#  mdadm --assemble /dev/md/debian:0  -v /dev/sdb2 --run
> mdadm: looking for devices for /dev/md/debian:0
> mdadm: /dev/sdb2 is identified as a member of /dev/md/debian:0, slot 1.
> mdadm: no uptodate device for slot 0 of /dev/md/debian:0
> mdadm: failed to add /dev/sdb2 to /dev/md/debian:0: Invalid argument

Bad checksum caused kernel to reject the device.

There is no obvious way to correct the checksum, but I think you can
force it by using the --update option to --assemble
e.g.

  mdadm --assemble /dev/md/debian:0 --update=name -v /dev/sdb2

When doing that, you should check that other fields all look correct
first, because something must have changed to affect the bitmap.
(I cannot see anything that looks wrong)

NeilBrown

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