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List:       evms-devel
Subject:    Re: [Evms-devel] RAID1 with one segment
From:       Kevin Corry <kevcorry () us ! ibm ! com>
Date:       2005-06-12 13:56:29
Message-ID: 200506120856.29447.kevcorry () us ! ibm ! com
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Hi Martin,

On Sun June 12 2005 3:22 am, Martin Frankel wrote:
> I am a brand new EVMS user. I am running evms 2.5.2 with
> 2.6.10-gentoo-r6 kernel. I have managed to wedge EVMS pretty thoroughly
> in about 15 minutes. I can no longer run the GUI or command line
> version. They both hang immediately, apparently during region discovery.
>
> As best I can tell, what got me in this pickle was trying to create a
> RAID1 region from a single segment in evmsgui. Yes, I know, not kosher.
> However the GUI didn't stop me and I wanted to see what would happen.
> When I clicked "Save," evmsgui segfaulted. Log is attached.

Well, there's no reason you shouldn't be able to create a 1-way RAID1. It 
obviously doesn't provide a lot of redundancy, but it's still a perfectly 
valid configuration. I'm not sure why the gui would be segfaulting on you in 
that situation.

> The docs really don't suggest a way out of a situation like this. If
> there were any data on this disk I'd really be sweating right now. As it
> stands I just did "dd if=/dev/zero of=/dev/hdb" which got me back in
> business.

Yeah, that would do it. The MD RAID superblocks are at the end of the disk, so 
it's not as easy to wipe them out as it is for, say, a DOS partition table or 
LVM PV signature, which are at the start.

> I must say this does not inspire confidence. It's a bummer because I was
> otherwise very impressed with EVMS. Any suggestions on what an end user
> should do in a situation like this with a production hard drive?

Sorry you've had so much trouble getting this running. Unfotunately, I'd need 
a more detailed log to really pinpoint the problem. If you have the time and 
can recreate this problem, run evmsgui with the "-d debug" option. If it 
still segfaults, email me a gzipped copy of the engine log and I'll take a 
look.

What I did notice in you log, however, was a number of activation failures for 
segments on hda. You're running a 2.6.10 kernel, so this is obviously a 
bdclaim issue. If you don't intend on using EVMS to manage your partitions  
on hda, you might want to add "hda" to the "sysfs_devices.exclude" list in 
your /etc/evms.conf file.

I'll also give this a try on my test box on Monday to see if I can reproduce 
the problem.

-- 
Kevin Corry
kevcorry@us.ibm.com
http://www.ibm.com/linux/
http://evms.sourceforge.net/


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