Re: create raid10 md raid which hangs on auto-read-only with resync=PENDING

[NeilBrown <neilb@suse.de>]

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On Thu, 03 May 2012 12:04:49 +0300 Nikolay Kichukov <hijacker@oldum.net>
wrote:

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> Hi all,
> I have recently included one more drive in my system and has switched from raid0 to raid10 on 3 devices/partitions.
> 
> I have created the raid as follows:
> 
> mdadm --create /dev/md3 --verbose --raid-devices=3 --level=raid10 --name=cryptdata  --layout=o2 --chunk=2M /dev/sda3
> /dev/sdb3 /dev/sdf3
> mdadm: size set to 319434752K
> mdadm: Defaulting to version 1.2 metadata
> mdadm: array /dev/md3 started.
> 
> 
> Information about the array:
> 
> mdadm --detail /dev/md3
> /dev/md3:
>         Version : 1.2
>   Creation Time : Thu May  3 11:42:57 2012
>      Raid Level : raid10
>      Array Size : 479152128 (456.96 GiB 490.65 GB)
>   Used Dev Size : 319434752 (304.64 GiB 327.10 GB)
>    Raid Devices : 3
>   Total Devices : 3
>     Persistence : Superblock is persistent
> 
>     Update Time : Thu May  3 11:42:57 2012
>           State : clean, resyncing (PENDING)
>  Active Devices : 3
> Working Devices : 3
>  Failed Devices : 0
>   Spare Devices : 0
> 
>          Layout : offset=2
>      Chunk Size : 2048K
> 
>            Name : hanna64:cryptdata  (local to host hanna64)
>            UUID : a7cc8eb7:8555b1bd:2856b686:829861be
>          Events : 0
> 
>     Number   Major   Minor   RaidDevice State
>        0       8        3        0      active sync   /dev/sda3
>        1       8       19        1      active sync   /dev/sdb3
>        2       8       83        2      active sync   /dev/sdf3
> 
> 
> And under /proc/mdstat:
> 
> cat /proc/mdstat
> Personalities : [raid0] [raid1] [raid10]
> md3 : active (auto-read-only) raid10 sdf3[2] sdb3[1] sda3[0]
>       479152128 blocks super 1.2 2048K chunks 2 offset-copies [3/3] [UUU]
>       	resync=PENDING
> 
> 
> The resync was not started due to the array being in auto-read-only mode.
> 
> I googled the issue and found out that to be able to start the resync one should issue:
> 
> mdadm --readwrite /dev/mdx
> (ref.: http://wiki.xtronics.com/index.php/Raid )
> 
> I have done it and it started resyncing:
> cat /proc/mdstat
> Personalities : [raid0] [raid1] [raid10]
> md3 : active raid10 sdf3[2] sdb3[1] sda3[0]
>       479152128 blocks super 1.2 2048K chunks 2 offset-copies [3/3] [UUU]
>       [=>...................]  resync =  6.2% (29748096/479152128) finish=120.3min speed=62220K/sec
> 
> 
> 
> Is this intended feature for 1.2 metadata?

This behaviour isn't a function of 1.2 metadata.
It is a function of  /sys/module/md_mod/parameters/start_ro which
is probably being setting by Debian early in boot because that can be a very
sensible thing to do.

I should probably get --create to over-ride it (I thought I had, but
obviously not).

If you write '0' to it, you'll find that the array starts normally.

Alternately, just start using the array.  As soon as you "mkfs", the array
will start resyncing.

NeilBrown


> 
> Kernel: 3.1.0-1-amd64
> mdadm: 3.2.3-2
> Distro: Debian testing
> 
> Cheers,
> - -Nik
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