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

[brem belguebli]

Hi Alfredo,
For the moment, it is a POC, and  I'm basing the whole thing on the RAID1
mdadm resource script I have submitted.

I'm also considering the possibility of using a Continuous Access (HP arrays
like EMC's SRDF functionnality) but still need raid manager binaries etc ...
and the time and inspiration to write the scripts.

Ideally, I would tend to privilege LVM mirror, but it still has some points
to be addressed as SPOF on mirrorlog etc...

Brem

2009/9/2 Moralejo, Alfredo <alfredo.moralejo at roche.com>

>  What kind of data replication will be used?
>
>
>
> Regards,
>
>
>
> Alfredo
>
>
>  ------------------------------
>
> *From:* linux-cluster-bounces at redhat.com [mailto:
> linux-cluster-bounces at redhat.com] *On Behalf Of *brem belguebli
> *Sent:* Wednesday, September 02, 2009 1:14 PM
> *To:* linux clustering
> *Subject:* [Linux-cluster] Re: Fencing question in geo cluster (dual sites
> clustering)
>
>
>
> 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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