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Re: [Linux-cluster] Networking guidelines for RHCS across datacenters



On 05/06/2009, at 6:52 PM, brem belguebli wrote:

Hello,

That sounds pretty much to the question I've asked to this mailing- list last May (https://www.redhat.com/archives/linux-cluster/2009-May/msg00093.html ).

We are in the same setup, already doing "Geo-cluster" with other technos and we are looking at RHCS to provide us the same service level.

Latency could be a problem indeed if too high , but in a lot of cases (many companies for which I've worked), datacenters are a few tens of kilometers far, with a latency max close to 1 ms, which is not a problem.

Let's consider this kind of setup, 2 datacenters far from each other by 1 ms delay, each hosting a SAN array, each of them connected to 2 SAN fabrics extended between the 2 sites.

What reason would prevent us from building Geo-clusters without having to rely on a database replication mechanism, as the setup I would like to implement would also be used to provide NFS services that are disaster recovery proof.

Obviously, such setup should rely on LVM mirroring to allow a node hosting a service to be able to write to both local and distant SAN LUN's.

Brem


I have been wondering whether the same could be done (cross-site RHCS) using SAN replication and multipath, avoiding LVM mirroring. This is going to depend strongly on the storage replication failover time; if the IO to shared storage devices is queued for too long, the cluster will stop. Does anyone have any experience with how quick this would need to happen for RHCS to tolerate it?

I have been meaning to test this but have not had a chance...

Tom


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