weird SparesMissing event

weird SparesMissing event

[Tobias Gunkel]

Hello everyone,

I've got a strange SparesMissing event on one of my raid1 arrays.
mdadm --detail /dev/md2 says all ok, but I get this message by mdadm
monitor every day:

A SparesMissing event had been detected on md device /dev/md2.

Faithfully yours, etc.

P.S. The /proc/mdstat file currently contains the following:

Personalities : [raid1]
md2 : active raid1 sda3[0] sdc3[2](S) sdb3[1]
      474714048 blocks [2/2] [UU]
[...]

root@MCI03:~# mdadm --detail /dev/md2
/dev/md2:
        Version : 0.90
  Creation Time : Fri May 28 14:54:26 2010
     Raid Level : raid1
     Array Size : 474714048 (452.72 GiB 486.11 GB)
  Used Dev Size : 474714048 (452.72 GiB 486.11 GB)
   Raid Devices : 2
  Total Devices : 3
Preferred Minor : 2
    Persistence : Superblock is persistent

    Update Time : Wed Aug 11 08:52:13 2010
          State : clean
 Active Devices : 2
Working Devices : 3
 Failed Devices : 0
  Spare Devices : 1

           UUID : 7aa24776:9d6e8d24:54307b3d:1949437b (local to host MCI03)
         Events : 0.985979

    Number   Major   Minor   RaidDevice State
       0       8        3        0      active sync   /dev/sda3
       1       8       19        1      active sync   /dev/sdb3

       2       8       35        -      spare   /dev/sdc3


This makes me wonder, too:

root@MCI03:~# mdadm --examine --scan
ARRAY /dev/md0 UUID=304f5f2a:fbc8082b:54307b3d:1949437b
   spares=1
ARRAY /dev/md1 UUID=b263f9c1:5c680152:54307b3d:1949437b
   spares=1
ARRAY /dev/md2 UUID=7aa24776:9d6e8d24:54307b3d:1949437b
   spares=2

Why spares=2 for md2? It was created during Debian system install with
spares=1.

root@MCI03:~# mdadm -V
mdadm - v3.0.3 - 22nd October 2009

root@MCI03:~# uname -r
2.6.32preemptive


What's wrong here?
Thanks for any comments!

Best regards, Tobi

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Re: weird SparesMissing event

[Neil Brown]

On Wed, 11 Aug 2010 09:04:32 +0200
Tobias Gunkel <tobias.gunkel@qumido.de> wrote:

> Hello everyone,
> 
> I've got a strange SparesMissing event on one of my raid1 arrays.
> mdadm --detail /dev/md2 says all ok, but I get this message by mdadm
> monitor every day:
> 
> A SparesMissing event had been detected on md device /dev/md2.

This means that /etc/mdadm/mdadm.conf says /dev/md2 has more spare devices
than it currently has.  What is in /etc/mdadm/mdadm.conf



> This makes me wonder, too:
> 
> root@MCI03:~# mdadm --examine --scan
> ARRAY /dev/md0 UUID=304f5f2a:fbc8082b:54307b3d:1949437b
>    spares=1
> ARRAY /dev/md1 UUID=b263f9c1:5c680152:54307b3d:1949437b
>    spares=1
> ARRAY /dev/md2 UUID=7aa24776:9d6e8d24:54307b3d:1949437b
>    spares=2
> 
> Why spares=2 for md2? It was created during Debian system install with
> spares=1.

What do you get if you run

 mdadm --examine --scan --verbose

it should add a 'devices=' line which will show you which devices it is
counting.

NeilBrown

Re: weird SparesMissing event

[Tobias Gunkel]

Am 11.08.2010 09:57, schrieb Neil Brown:
> This means that /etc/mdadm/mdadm.conf says /dev/md2 has more spare devices
> than it currently has.  What is in /etc/mdadm/mdadm.conf

root@MCI03:~# egrep -v '^#|^$' /etc/mdadm/mdadm.conf
DEVICE partitions
CREATE owner=root group=disk mode=0660 auto=yes
HOMEHOST <system>
ARRAY /dev/md0 UUID=304f5f2a:fbc8082b:54307b3d:1949437b
   spares=1
ARRAY /dev/md1 UUID=b263f9c1:5c680152:54307b3d:1949437b
   spares=1
ARRAY /dev/md2 UUID=7aa24776:9d6e8d24:54307b3d:1949437b
   spares=2
MAILADDR foo@bar.com


> What do you get if you run
> 
>  mdadm --examine --scan --verbose

root@MCI03:~# mdadm --examine --scan --verbose
ARRAY /dev/md0 level=raid1 num-devices=2
UUID=304f5f2a:fbc8082b:54307b3d:1949437b
   spares=1   devices=/dev/sdc1,/dev/sdb1,/dev/sda1
ARRAY /dev/md1 level=raid1 num-devices=2
UUID=b263f9c1:5c680152:54307b3d:1949437b
   spares=1   devices=/dev/sdc2,/dev/sdb2,/dev/sda2
ARRAY /dev/md2 level=raid1 num-devices=2
UUID=7aa24776:9d6e8d24:54307b3d:1949437b
   spares=2
devices=/dev/sdc3,/dev/sdc,/dev/sdb3,/dev/sdb,/dev/sda3,/dev/sda


Hm, md2 contains devices. How is that?

Tobi

Re: weird SparesMissing event

[Neil Brown]

On Wed, 11 Aug 2010 11:46:22 +0200
Tobias Gunkel <tobias.gunkel@qumido.de> wrote:

> Am 11.08.2010 09:57, schrieb Neil Brown:
> > This means that /etc/mdadm/mdadm.conf says /dev/md2 has more spare devices
> > than it currently has.  What is in /etc/mdadm/mdadm.conf
> 
> root@MCI03:~# egrep -v '^#|^$' /etc/mdadm/mdadm.conf
> DEVICE partitions
> CREATE owner=root group=disk mode=0660 auto=yes
> HOMEHOST <system>
> ARRAY /dev/md0 UUID=304f5f2a:fbc8082b:54307b3d:1949437b
>    spares=1
> ARRAY /dev/md1 UUID=b263f9c1:5c680152:54307b3d:1949437b
>    spares=1
> ARRAY /dev/md2 UUID=7aa24776:9d6e8d24:54307b3d:1949437b
>    spares=2
> MAILADDR foo@bar.com

As I thought, mdadm.conf says to expect 2 spares, but there is really only
one.  Just edit the file and the message will stop.

> 
> 
> > What do you get if you run
> > 
> >  mdadm --examine --scan --verbose
> 
> root@MCI03:~# mdadm --examine --scan --verbose
> ARRAY /dev/md0 level=raid1 num-devices=2
> UUID=304f5f2a:fbc8082b:54307b3d:1949437b
>    spares=1   devices=/dev/sdc1,/dev/sdb1,/dev/sda1
> ARRAY /dev/md1 level=raid1 num-devices=2
> UUID=b263f9c1:5c680152:54307b3d:1949437b
>    spares=1   devices=/dev/sdc2,/dev/sdb2,/dev/sda2
> ARRAY /dev/md2 level=raid1 num-devices=2
> UUID=7aa24776:9d6e8d24:54307b3d:1949437b
>    spares=2
> devices=/dev/sdc3,/dev/sdc,/dev/sdb3,/dev/sdb,/dev/sda3,/dev/sda
> 
> 
> Hm, md2 contains devices. How is that?

Partition3 on each device must start at a multiple of 64K and extend to then
end of the device.  In this case both the partition and the whole device
appear to have the same metadata, and mdadm cannot tell which is correct.
This is a short-coming of v0.90 metadata and is fixed in v1.x.
You can avoid this by changing the 'device' line in mdadm.conf to

   DEVICE /dev/sd*[0-9]

which essentially means "only partitions of sd devices should be considered
for membership in md arrays".

NeilBrown


> 
> Tobi
> --
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Re: weird SparesMissing event

[Tobias Gunkel]

Am 11.08.2010 13:09, schrieb Neil Brown:

> As I thought, mdadm.conf says to expect 2 spares, but there is really only
> one.  Just edit the file and the message will stop.

Yes, now it's all fine, thanks!

But mdadm --examine --scan --verbose still shows spares=2:

ARRAY /dev/md2 level=raid1 num-devices=2
UUID=7aa24776:9d6e8d24:54307b3d:1949437b
   spares=2
devices=/dev/sdc3,/dev/sdc,/dev/sdb3,/dev/sdb,/dev/sda3,/dev/sda

...although mdadm.conf was updated:

grep -A1 md2 /etc/mdadm/mdadm.conf
ARRAY /dev/md2 UUID=7aa24776:9d6e8d24:54307b3d:1949437b
   spares=1


Tobi