[ClusterLabs] Antw: Re: Antw: Re: DLM fencing

[Digimer]

On 11/02/16 02:37 AM, Ulrich Windl wrote:
>>>> Digimer <lists at alteeve.ca> schrieb am 10.02.2016 um 17:32 in Nachricht
> <56BB6637.6090802 at alteeve.ca>:
>> On 10/02/16 02:40 AM, Ulrich Windl wrote:
> 
> [...]
>>>> If fencing fails or is not configured, DLM never unblocks and anything
>>>> using it is left hung (by design, better to hang than risk corruption).
>>>>
>>>> One of many reasons why fencing is critical.
>>>
>>> I'm not deeply in DLM, but it seems to me DLM can run standalone, or in the
>>> cluster infrastructure (we only use it inside the cluster). When running
>>> standalone, it makes sense that DLM has ist own fencing, but when running
>>> inside the cluster infrastructure, I'd expect tha tthe cluster's fencing
>>> mechanisms are used (maybe just because if the better logging of reasons).
>>
>> To be clear; DLM does NOT have it's own fencing. It relies on the
>> cluster's fencing.
> 
> OK, is this true for cLVM and O2CB as well? I always felt some of those is doing a fencing themselves as soon as they fail to communicate with DLM. So the first guess was it's DLM...

I can't speak to o2cb, never used it. However, clustered LVM, gfs2 and
rgmanager use DLM, and in all cases, DLM does nothing but block until it
is told that the fence was successful. It plays no active role in fencing.

-- 
Digimer
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