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Re: [Linux-cluster] Graceful recover after connectivity failure

On Tue, 15 Jan 2008, Cliff Hones wrote:

Fajar A. Nugraha wrote:
AFAIK the prequisite for a cluster of any kind (be it RHEL or RAC) is that you have a failure-resistant network. This can be achieved for example by using dedicated heartbeat switches or cross-cables (in case of two nodes), plus ethernet bonding (in linux) for redundancy.

While I understand your requirement, I don't think an environment with (possibly) unreliable n/w is a good place for a cluster. Perhaps a simple thin client is more appropriate.

We actually have two areas in which we wanted to use GFS - one is an
office environment where the network, while not unreliable, is subject
to occasional reconfiguration as machines/switches are moved.  The other
is a datacentre environment where the infrastructure should be resilient.

In both cases, our primary need for clustering is to enable GFS to be
used.  Our local office setup could dispense with GFS/clustering and
we could use other data sharing solutions such as NFS; however, we
were planning to use a common solution so as to minimise maintenance
costs and maximise our familiarity with the technology.

Are you saying that you are planning to use cluster / GFS across more than one switch (or a redunddant pair thereof)? That is quite unusual, as the performance would likely suffer.

If you require operation under unreliable conditions, you should probably look into using NFS over UDP, or for more transparent outages, Coda. Coda supports disconnected operation and files get cached locally on the clients. Provided multiple writers don't end up clobbering each other's files often during disconnection (which usually leads to a requirement for manual conflict resolution), you may find that it is a better solution for you than clustering.

Remember that GFS, NFS/CIFS and Coda are designed for three distinctly different environments. If you are thinking about using GFS for connecting desktops to the shared storage just to use the same technology for everything, not only is that the wrong tool for the job, it will stop working as soon as 1/2 of the machines are switched off/disconnected.


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