WARNING - OLD ARCHIVES

This is an archived copy of the Xen.org mailing list, which we have preserved to ensure that existing links to archives are not broken. The live archive, which contains the latest emails, can be found at http://lists.xen.org/
   
 
 
Xen 
 
Home Products Support Community News
 
   
 

xen-users

[Xen-users] Re: [Linux-HA] Xen EVMS-HA mini-howto and locking mechanism

To: "Robert Wipfel" <rawipfel@xxxxxxxxxx>, jdebaer@xxxxxxxxxx
Subject: [Xen-users] Re: [Linux-HA] Xen EVMS-HA mini-howto and locking mechanism remark
From: "Tijl Van den Broeck" <subspawn@xxxxxxxxx>
Date: Thu, 4 Jan 2007 14:25:13 +0100
Cc: evms-cluster@xxxxxxxxxxxxxxxxxxxxx, linux-ha@xxxxxxxxxxxxxxxxxx, xen-users@xxxxxxxxxxxxxxxxxxx
Delivery-date: Thu, 04 Jan 2007 05:25:07 -0800
Domainkey-signature: a=rsa-sha1; q=dns; c=nofws; s=beta; d=gmail.com; h=received:message-id:date:from:to:subject:cc:in-reply-to:mime-version:content-type:content-transfer-encoding:content-disposition:references; b=WaumjB1GWc75B+EkMcTiB9+3Rz+7Njrf9F3+mQ+wV/Ky8bz0RTGLxN7ybq3kltpW6wjcRbtnTzfXmAJ1Pj9mc0dDbBj/aG8rO5gMuHZs2R7L5tUke2PBZ4L1hvc/bpz8PoGv4L34tLedhS/t6o/UBJpeVV58/lmmtVgxUkT2+Lc=
Envelope-to: www-data@xxxxxxxxxxxxxxxxxx
In-reply-to: <459C7324020000CF000225F3@xxxxxxxxxxxxxxxxxxxxxxxxx>
List-help: <mailto:xen-users-request@lists.xensource.com?subject=help>
List-id: Xen user discussion <xen-users.lists.xensource.com>
List-post: <mailto:xen-users@lists.xensource.com>
List-subscribe: <http://lists.xensource.com/cgi-bin/mailman/listinfo/xen-users>, <mailto:xen-users-request@lists.xensource.com?subject=subscribe>
List-unsubscribe: <http://lists.xensource.com/cgi-bin/mailman/listinfo/xen-users>, <mailto:xen-users-request@lists.xensource.com?subject=unsubscribe>
References: <459C7324020000CF000225F3@xxxxxxxxxxxxxxxxxxxxxxxxx>
Sender: xen-users-bounces@xxxxxxxxxxxxxxxxxxx
Robert & Jo,

Thank you very much for this information, it clarifies a lot.
To create a failsafe environment, in which virtual machines cannot
ever be double booted.
Either a shared cluster filesystem (such as OCFS2) is required as
backend (in which OCFS2 provides locking) or a Xen-vm resource for HA
with a shared raw I/O backend device, in which heartbeat fully
controls and prevents the duplicates of a Xen-vm. This is in anyhow
the great pointer I was looking for.

I'll try to keep the lists and Xensource wiki updated of any progress made.

greetings

Tijl Van den Broeck



On 1/4/07, Robert Wipfel <rawipfel@xxxxxxxxxx> wrote:
Tijl,

Jo De Baer has been adding some information about shared
cluster containers, for OCFS2 and Xen, at this Wiki
http://wiki.novell.com/index.php/SUSE_Linux_Enterprise_Server#High_Availability_Storage_Foundation
==
First preview release - November 15 2007 : download here
This preview release shows how to integrate a EVMS2 shared cluster container
==

In response to your question about Xen using EVMS cluster containers...
EVMS itself doesn't do any locking that would protect a container on one node
from concurrent access by a different node. Cluster containers work by
masking access - the EVMS devnodes should only be visible on one node at
a time - as a function of the failover manager managing EVMS to mask /
unmask the devnodes across nodes (for private containers). Shared cluster
containers are visible on all nodes, with the expectation highler layer
software (e.g. a cluster file system) is sharing and coordinating access
to that shared storage.

Whether or not the same Xen VM is active on more than one cluster
node at a time, is also provided by Heartbeat's management of Xen VMs
as cluster resources - it's Heartbeat's job to ensure the same resource
(VM) isn't running in two places at the same time.

(Xen knows whether the same block device is being accessed by more
than one VM on the same server - and protects against that).

Hth,
Robert



_______________________________________________
Xen-users mailing list
Xen-users@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-users

<Prev in Thread] Current Thread [Next in Thread>