[ClusterLabs] Fencing with a 3-node (1 for quorum only) cluster

[Jan Pokorný]

On 15/08/16 14:48 +0200, Jan Pokorný wrote:
>> On 04/08/16 07:21 PM, Dan Swartzendruber wrote:
>>> On 2016-08-04 19:03, Digimer wrote:
>>>> As for DRAC vs IPMI, no, they are not two things. In fact, I am pretty
>>>> certain that fence_drac is a symlink to fence_ipmilan. All DRAC is (same
>>>> with iRMC, iLO, RSA, etc) is "IPMI + features". Fundamentally, the fence
>>>> action; rebooting the node, works via the basic IPMI standard using the
>>>> DRAC's BMC.
>>>> 
>>>> [...]
>>> 
>>> At least on CentOS7, fence_ipmilan and fence_drac are not the same.
>>> e.g. they are both python scripts that are totally different.
>> 
>> [...] 
>> 
>> As for the two agents not being symlinked, OK. It still doesn't change
>> the core point through that both fence_ipmilan and fence_drac would be
>> acting on the same target.
> 
> Just thought I'd add some clarifications:
> 
> - in fact fence-agents upstream seems to have thrown the idea of
>   proper symlinks away before functionality to that effect was added,
>   eventually using file copies instead of symlinks, with the rationale
>   "this approach is not recommended so they regular files"

    Reference needed (accidentally omitted):
    https://github.com/ClusterLabs/fence-agents/commit/87266bc

>   [Marx&Oyvind, I cannot really imagine what issues this was meant to
>   solve nor why it would be not recommended (in Pacemaker, stat calls
>   are used that work with symlink targets, not the immediate link
>   files, ditto other standard file handling functions), but it seems
>   pretty non-systemic compared to, e.g., fence_xvm -> fence_virt:
>   https://github.com/ClusterLabs/fence-virt/blob/f1f1a2437c5b0811269b5859a5ef646f44105a88/client/Makefile.in#L39
>   and this also makes resulting packages inflated with redundant
>   scripts + man pages needlessly;  I'd make a PR for that but it
>   seems premature until the recursive make/install issue with
>   "symlinked" agents has a definitive conclusion (PR 81+82), but
>   basically, you just want 'ln -s SRC DST' instead of 'cp SRC DST']
> 
> - fence_ipmilan and fence_drac are indeed not even virtually
>   symlinked; quick and dirty way to receive this information, see
>   https://bugzilla.redhat.com/show_bug.cgi?id=1210679#c12
>   (you may need ' | tr -s " "' just after 'ls -l' command)
>   from where you can see that it is fence_idrac which is a virtual
>   symlink (same implementation) as fence_ipmilan, while fence_drac
>   is an agent on its own
> 
> 
> Hope this helps.

-- 
Jan (Poki)
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