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Re: [Linux-cluster] Adding a node back to cluster failing



On 04/11/13 11:18, David Teigland wrote:
> On Mon, Nov 04, 2013 at 09:31:08AM -0500, Digimer wrote:
>>>>> We are having a node two cluster with manual fencing configuration .
>>>>
>>>> An HA cluster with manual fencing is no cluster at all.
>>>
>>> No. It is a cluster. But it provides no high availability.
>>
>> Let me echo Zama and Michael.
>>
>>   Clusters without real fencing are not supported. Manual fencing was
>> dropped because it's not reliable and it is way too easy for mistakes to
>> happen.
>>
>>   Please add real fencing. Test it to make sure it works. I expect
>> things will start working fine then and you will have no trouble joining
>> a node back to your cluster.
> 
> The dogmatic attitude against manual fencing is disturbing.  It is a
> perfectly legitimate and useful way to run a cluster as long as it's used
> appropriately and with an understanding of how it works, the limitations
> and tradeoffs.
> 
> Dave

https://access.redhat.com/site/articles/28601

===
Fence Agent 	RHEL 5		RHEL 6
manual		no [3]		no
===

[3] - fence_manual is shipped in Red Hat Enterprise Linux 4 and Red Hat
Enterprise Linux 5, but it is not supported. See RHEL High Availability:
Manual Fencing (fence_manual vs. fence_ack_manual) for details on
fence_manual vs. fence_ack_manual.

That links to:

https://access.redhat.com/site/node/36302

===
Usage of the fence agent fence_manual implies that every time a node
fails in your cluster, it will always require manual intervention to
continue cluster operations, including the ability to relocate a failed
service to a functional node. This is the reason that fence_manual is
unsupported since it does not provide for high availability unless you
have a system administrator monitoring your cluster 24 hours a day. In
addition, it can cause corruption of cluster resources if used incorrectly.
===

This seems like a very good reason to have a "dogmatic" opposition to
manual fencing. Red Hat doesn't support it and mis-use can cause data
corruption and loss. Given how poorly most people understand fencing's
role, it's just asking for trouble.

So I stand by my (very strong) recommendation against manual fencing.

-- 
Digimer
Papers and Projects: https://alteeve.ca/w/
What if the cure for cancer is trapped in the mind of a person without
access to education?


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