# md0 "capacity change" and "unkown partition table"

## c00l.wave

I updated my kernel from 2.6.25-r7 to 2.6.31-r6 (gentoo-sources). I'm now seeing these messages every time I boot my system:

```

raid1: raid set md0 active with 2 out of 2 mirrors                                                                                                           

md0: detected capacity change from 0 to 536869404672                                                                                                         

md: ... autorun DONE.                                                                                                                                        

 md0: unknown partition table

```

I didn't change anything on the RAID or any partition, md0 is being recognized and mounted correctly without becoming degraded.

```

# mdadm --detail /dev/md0

/dev/md0:

        Version : 0.90

  Creation Time : Mon Apr 14 02:55:34 2008

     Raid Level : raid1

     Array Size : 524286528 (500.00 GiB 536.87 GB)

  Used Dev Size : 524286528 (500.00 GiB 536.87 GB)

   Raid Devices : 2

  Total Devices : 2

Preferred Minor : 0

    Persistence : Superblock is persistent

    Update Time : Fri Dec 11 23:34:28 2009

          State : clean

 Active Devices : 2

Working Devices : 2

 Failed Devices : 0

  Spare Devices : 0

           UUID : a4b24559:cd98291a:a5d98e37:1e73f3cc

         Events : 0.309834

    Number   Major   Minor   RaidDevice State

       0       8       18        0      active sync   /dev/sdb2

       1       8       34        1      active sync   /dev/sdc2

```

Should I worry about these errors? Do I have to update the RAID version somehow? Anyone knows what's wrong and how I can fix it? I thought this may fix itself after a reboot (md0 metadata being updated by the kernel or similar) or the RAID may eventually fail. Neither happened, it's just these strange messages when booting.

----------

## c00l.wave

It's the same on my servers. The server RAIDs were created remotely from a Debian based rescue system (no other way to install Gentoo) with metadata version 0.90 (same as on my workstation). 2.6.30 already complained about "unknown partition table", 2.6.31 now starts seeing changed sizes.

The manpage of mdadm says I could update size information but only for more recent metadata versions. Should I update the RAID's metadata in some way? Is this even possible or do I have to degrade, recreate, copy and sync to initialize a whole new array? Are there any issues using a recent kernel with metadata version 0.90?

Edit: mdadm is at version 3.0.

----------

## RottenMutt

i'm in same boat (except i created this array on this system after installation but i think i got a recent udev update), should i do anything?  my guess is yes, may help recovering a failed array in the future.

```
md0: detected capacity change from 0 to 6001191813120

 md0: unknown partition table
```

----------

## c00l.wave

I haven't done anything yet and it's still working and resyncing if needed.  :Smile: 

I guess the message about the capacity change is caused by the old md metadata which just may not have contained that information. There doesn't seem to be a way to simply update the metadata to a newer version, so we will have to stick with it (maybe that's better considering compatibility with older rescue CDs/images etc.).

The message about the partition table may not be related to md at all. I assume that the kernel only does the usual check for partition tables on block devices after a md RAID device comes online. Since you are able to put a partition table inside md, that's just what should happen. Anyway, the message is still confusing. I decided to ignore the messages and didn't check any further.

Edit: I just grepped the kernel source code: Both messages seem to be unrelated to md and generic for block devices.

----------

## energyman76b

I get the same messages, I didn't do anything about it, when raid1 needed resync it worked just fine.

If it works, don't touch it.

----------

## drescherjm

I get the same message on my dozen or so mdadm raid arrays here at work. It is harmless. Well at least I have never experienced any issue related to this..

----------

## drizzt

Well the system is right as always.   :Wink: 

On time of detection the size changes from '0' to x bytes due to added drives. If you would add drivers at runtime (and increase the total space available to the raid) you would get the same message with different values(from x to y bytes).

For the other message I found a page long time ago where it states that the kernel subsystem tries to read the partition table from the not (yet)existing raid (no discs -> no partition table).

Nothing to worry about. Totally normal behaviour.

regards

----------

