On 2018-02-13 05:46 AM, Maxim wrote:
> 12.02.2018 19:31, Digimer пишет:
>> Without fencing, all bets are off. Please enable it and see if the
>> issue remains
> Seems, i know [in theory] about the fencing ability and its importance
> (although I've never configured it so far).
> But i don't undestand how it would help in the situtions of the hard
An availability cluster's job is to keep things running. To do this,
there must be coordination between the nodes (otherwise, just run things
everywhere and be done with it). Thus, when a node stops responding, it
is critical that the lost node be put into a known state.
If you allow assumptions to be made, you will eventually assume wrong.
That could have consequences as "minor" as confusing switches/routers to
as devastating as corrupted data.
Fencing is not meant to speed up recovery, it is critical to ensuring
recovery works at all.
This is a common confusion (and people often mistakenly think that
quorum is how you avoid this, which is incorrect). There is no
replacement for fencing; You need it in any availability system. Without
it, it is like driving without a seat-belt.
>> Changing EL6 to corosync 2 pushes further into uncharted waters. EL6
>> should be using the cman pluging with corosync 1. May I ask why you
>> don't use EL7 if you want such a recent stack?
> For historical reasons. Let's say so. I've another software that built
> for RHEL 6 like OS and have to be installed on the cluster node.
> EL 7 stack is already not so recent, but it's one the most stable and
> least vulnearable, i suppose. And i understand the risks.
> I will update pcs to the latest version when i find a bit of free time.
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