Re: [Evms-devel] Possible to create a degraded RAID5 array with EVMS?

[James L. <jam...@ho...>]

Hi there,

I'm having some more trouble with getting EVMS and mdadm to play nicely 
together (even after upgrading EVMS)...

The steps I'm taking are:

1. Starting with an empty drive (wiped it by zero-filling the start and end 
of drive to make sure there's no residual partition table information).  
Create two logical partitions (/dev/sdb5 and /dev/sdb6).

2. Use mdadm to create a degraded "3-drive" RAID5 array called /dev/md0: 
"mdadm --create /dev/md0 --level=5 --raid-devices=3 /dev/sdb5 /dev/sdb6 
missing".

3. Start EVMS.  It correctly detects the degraded RAID5 array on /dev/md0.

4. In EVMS, create 4 partitions on /dev/sdb, each one just over half the 
size of the partitions in the RAID5 array.  Create two 2-drive RAID0 
stripes, from these partitions.

5. Add one of these RAID0 arrays to the RAID5 array.  Wait for it to resync. 
  RAID5 array is now active and non-degraded.

6. Create an EXT3 filesystem and bung some files on it.

7. Everything working fine so far.  Now expand the RAID5 array with the 
other RAID0 array.  This seems to work fine.  No data lost on the partition 
and no errors.

8. Reboot.  When next starting EVMS, I get the following errors:

MDRaid5RegMgr: RAID5 array md/md0 is missing the member with RAID index 2.  
The array is running in degrade mode.

MDRaid5RegMgr: Region md/md0 is currently in degraded mode.  To bring it 
back to normal state, add 1 new spare device to replace the faulty or 
missing device.

Engine: Error code 5 (Input/output error) when reading the primary copy of 
feature on object md/md0

Engine: Error code 5 (Input/output error) when reading the secondary copy of 
feature on object md/md0


This is despite the fact that both the RAID0 array (as well as all the other 
hard drive partitions) are reported as OK by EVMS.  The EXT3 partition on 
the drive is no longer recognized.  Strangely, mdadm seems to be getting 
confused as well.  When examining the md arrays, it's reporting /dev/md0 and 
/dev/md1 as RAID0 arrays, and /dev/md2 as the RAID5 array (which is the 
wrong way round).

I've attached the evms engine log (no memory tracing though, sorry), and the 
output showing what mdadm thinks is going on (which seems odd).

I'm running the latest EVMS 2.5.3-7 on Ubuntu Breezy by the way.  Any ideas 
on this one?  Just when I thought I'd finished seeing problems with EVMS and 
mdadm, this comes along... doh!

Cheers,
James