[Linux-cluster] Re: Linux-cluster Digest, Preventing LVM from concurrent access

[David Hollister]

We use HA-LVM in environments where we do not use GFS. It works well in preventing shared storage from being mounted on both nodes simultaneouly. However I am not sure how it would react in a split brain conditon, which appears to be what you are describing. . You should probably consider creating redundancy in your heartbeat via IP Bonding. Basically having two nics on each host bound to one ip.
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From: linux-cluster-request at redhat.com

Date: Sun, 23 Aug 2009 12:00:08 
To: <linux-cluster at redhat.com>
Subject: Linux-cluster Digest, Vol 64, Issue 37


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Today's Topics:

   1. Preventing LVM from concurrent access (Edson Marquezani Filho)


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Message: 1
Date: Sun, 23 Aug 2009 12:35:39 -0300
From: Edson Marquezani Filho <edsonmarquezani at gmail.com>
Subject: [Linux-cluster] Preventing LVM from concurrent access
To: linux-cluster at redhat.com
Message-ID:
	<2fc5f090908230835p20acd5e0ya2bd2a3ba909350b at mail.gmail.com>
Content-Type: text/plain; charset=ISO-8859-1

Hello,

I'm a begginer on that cluster stuff, so I ask you for help.

I'm setting up a environment with virtual machines running upon Xen,
two servers, and a SAN storage. I want to set up a very simple
high-availability scenario, where once my master server goes down,
slave creates again those virtual machines on it. (What would
correspond to a restart of all machines, off course.)

Ok, I could do that with Heartbeat, with a very simple configuration
based on its version 1. It worked as expected.

My problem now is related to SAN data access.

I want to prevent data to be simultaneously mounted by both servers,
in a situation when I don't have master server down, altough it could
look like this. I'm connecting servers through a crossover UTP cable.
If it get disconnected or any of those dedicated interfaces goes down,
slave server would think that master server is down, and would
recreate all my virtual machines, altough it isn't down, corrupting
LVM and filesystem data.

Alright, I have found out that I would have to use either HA-LVM or
CLVMD. Actually, I think that HA-LVM would be more appropriate to me,
accordingly to what I've seen around. But, I'm really not sure about
that.

What should I use, exactly? Does HA-LVM do what I want? Does it
prevent LVM volumes from being mounted by more than a node
simultaneously? I have thought about locking VGs on each server, with
CLMD, but I'm not sure if it is the correct way for that.

I can say for sure that I just need data access at one server at a time.

What would be the simplest and more correct way for doing this?

Thank you.



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