[CentOS] Question about clustering

Mon Jun 16 14:08:51 UTC 2014
Digimer <lists at alteeve.ca>

No. For fencing to be worthwhile, it *must* work when the node is in any 
state. For this, it must be independent of node. A great way to see why 
is to test crashing the node (echo c > /proc/sysrq-trigger) or simply 
cutting the power to the node. With the node totally disabled, the 
surviving peer will fail to fence and, not being allowed to make 
assumptions, block.

On 16/06/14 05:39 AM, Alessandro Baggi wrote:
> Hi Digimer,
> there is a chance to make fencing without hardware, but only software?
> Il 15/06/2014 17:28, Digimer ha scritto:
>> On 15/06/14 08:54 AM, Alessandro Baggi wrote:
>>> Another question is about fencing. I've ridden that a cluster must have
>>> fencing to be considered as such. On CentOS 6.5 there is stonith that
>>> concerns node level fencing. For this type of fencing I must have ilo,
>>> ilom, drac, and other. It's possible to have fencing without Light-out
>>> devices, blade power control device and other? There are other device
>>> that can be used for fencing? Supposing a 2 node cluster with two server
>>> assembled (no hp, dell, sun, ibm..) how I can implement fencing with
>>> stonith? I can run a cluster without fencing and what implies do not use
>>> fencing?
>> A lot of odd problems go away once fencing is working. So this is a good
>> time to sort this out, then go back and see if your problems remain.
>> A very good way to fence machines without IPMI (etc) is to use an
>> external switched PDU, like the APC AP7900 (or your country version on).
>> http://www.apc.com/resource/include/techspec_index.cfm?base_sku=ap7900
>> If your budget is tight, I have seen these models frequently go on sale
>> for ~$200 (Canadian).
>> These work be allowing another node to log into the PDU and turn off the
>> power going to the lost/failed node. Please do note that the brand of
>> switched PDU you buy matters. For a device to work for fencing, it must
>> be possible for the cluster to talk to it. This is done using a "fence
>> handler", and there are many types that are supported (APC, Eaton, etc).
>> So if you want to get a different make/model, please first make sure
>> there is a fence handler.
>> Once you get this setup, see if your problems remain. If so, there is a
>> good clustering mailing list at:
>> https://www.redhat.com/mailman/listinfo/linux-cluster
>> And if you're on freenode, #linux-cluster is also very good.
>> Cheers!
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