Re: Backup Server RAID Array Event Notification

[NeilBrown <neilb@suse.de>]

On Thu, 9 Jun 2011 14:01:34 -0500 "Leslie Rhorer" <lrhorer@satx.rr.com> wrote:

> > -----Original Message-----
> > From: Roman Mamedov [mailto:rm@romanrm.ru]
> > Sent: Thursday, June 09, 2011 1:47 PM
> > To: lrhorer@satx.rr.com
> > Cc: linux-raid@vger.kernel.org
> > Subject: Re: Backup Server RAID Array Event Notification
> > 
> > On Thu, 9 Jun 2011 13:35:59 -0500
> > "Leslie Rhorer" <lrhorer@satx.rr.com> wrote:
> > 
> > >
> > > 	After I created a pair of two member RAID1 arrays and then added
> > > them as members to a RAID6 array, I am now getting messages similar to
> > the
> > > following, complaining of "Wrong-level" issues.  When I check the RAID6
> > > array, however, it is clean and both RAID1 members are still there.
> > When I
> > > check both RAID1 arrays, they show clean with no events.  I am running a
> > > compare between all the data on this machine and its mirror (this is a
> > > backup machine).  So far everything looks good.  What does this imply?
> > Is
> > > there something about which I should be worried?
> > 
> > You said RAID1 twice, and your mdadm --detail doesn't agree with you and
> > says
> > "raid0" twice. Maybe you mistakenly used RAID1 instead of RAID0 somewhere
> > else as well, and the WrongLevel message is trying to tell you that?
> 
> 	No, that was just a typo.  (OK, three typos) I meant "RAID0".  The
> RAID0 members are all 1T drives.  The RAID6 array is made of 1.5T members.
> In order to use the 1T drives on the RAID6 array, I have to combine them
> into 2T arrays, which then can be used as members of the RAID6 array.  If
> md10 and md11 were RAID1 arrays, they would only be 1T in extent, and could
> not be members of md0.
> 

"mdadm --monitor" does not monitor RAID0 or Linear arrays.  There is nothing
to see.  Nothing can fail, they don't rebuilt, they are really just AID, not
RAID.

So if it thinks that it was asked to monitor a RAID0 it pretends that it has
disappeared with reason "Wrong Level".
So if you explicitly ask it to monitor a RAID0, it won't and it will tell you
why.

If you only implicitly ask with e.g. "mdadm --monitor --scan" with a RAID0
listing in mdadm.conf it probably shouldn't give the message as it might be
confusing... but it does.
Or maybe the message is just confusing and I should change it.

Or something.

NeilBrown