[Linux-cluster] Re: Fencing question in geo cluster (dual sites clustering)

[brem belguebli]

Hi,

Any idea or comment on this.

Thanks

Brem
<http://1.bp.blogspot.com/_mz9iIrpv_qo/Si1NmQ2QNmI/AAAAAAAADP4/fV8j_ZsGlBw/s1600-h/Drawing1.png>


CF link attached to diagram that describes the setup.
http://1.bp.blogspot.com/_mz9iIrpv_qo/Si1NmQ2QNmI/AAAAAAAADP4/fV8j_ZsGlBw/s1600-h/Drawing1.png

2009/8/21, brem belguebli <brem.belguebli at gmail.com>:
>
> Hi,
>
> I'm trying to find out what best fencing solution could fit a dual sites
> cluster.
>
> Cluster is equally sized on each site (2 nodes/site), each site hosting a
> SAN array so that each node from any site can see the 2 arrays.
>
> Quorum  disk (iscsi LUN) is hosted on a 3rd site.
>
> SAN and LAN using the same telco infrastructure (2 redundant DWDM loops).
>
> In case something happens at Telco level (both DWDM loops are broken) that
> makes 1 of the 2 sites completely isolated from the rest of the world,
> the nodes at the good site (the one still operationnal) won't be able to
> fence any node from the wrong site (the one that is isolated) as there is no
> way for them to reach their ILO's or do any SAN fencing as the switches at
> the wrong site are no more reachable.
>
> As qdiskd is not reachable from the wrong nodes, they end up being rebooted
> by  qdisk, but there is a short time (a few seconds) during which the wrong
> nodes are still seing their local SAN array storage and may potentially have
> written data on it.
>
> Any ideas or comments on how to ensure data integrity in such setup ?
>
> Regards
>
> Brem
>
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