[Linux-HA] Understanding the behavior of IPaddr2 clone

[William Seligman]

On 2/27/12 5:49 PM, Lars Ellenberg wrote:
> On Mon, Feb 27, 2012 at 05:41:09PM -0500, William Seligman wrote:
>>>>> is this not *the* use case of globally-unique=true?
>>>>
>>>> I did not know about globally-unique. I just tested it, replacing (with name
>>>> substitutions):
>>>>
>>>> clone ipaddr2_clone ipaddr2_resource meta notify="true"
>>>>
>>>> with
>>>>
>>>> clone ipaddr2_clone ipaddr2_resource meta globally-unique="true"
>>>>
>>>> This fell back to the old behavior I described in the first message in this
>>>> thread: iptables did not update when I took down one of my nodes.
>>>>
>>>> I expected this, since according to "Pacemaker Explained",
>>>> globally-unique="true" is the default. If this had worked, I never would have
>>>> reported the problem in the first place.
>>>>
>>>> Is there something else that could suppress the behavior you described for
>>>> globally-unique=true?
>>>>
>>>
>>> You need clone-node-max == clone-max.
>>>
>>> It defaults to 1.
>>>
>>> Which obviously prevents nodes already running one
>>> instance from taking over an other...
>>
>> I tried it, and it works. So there's no need for my patch. The magic invocation
>> for a highly-available IPaddr2 resource is:
>>
>> ip_clone ip_resource meta clone-max=2 clone-node-max=2
> 
> Note that, if you have more than two nodes, to get more evenly
> distributed buckets in the case of failover, you can also specify larger
> numbers than you have nodes.  In which case by default, all nodes would
> run several.  And in case of failover, each remaining node should
> takeover it's share.
> 
>> Could this please be documented more clearly somewhere?
> 
> Clusters from Scratch not good enought?
> 
> http://www.clusterlabs.org/doc/en-US/Pacemaker/1.1/html/Clusters_from_Scratch/ch08s06.html

Drat and darnit, somehow I missed that page! Mea maxima culpa.

> But yes, I'll add a note to the IPaddr2 meta data
> where the long desc talks about cluster IP usage...
> 
> 


-- 
Bill Seligman             | Phone: (914) 591-2823
Nevis Labs, Columbia Univ | mailto://seligman@nevis.columbia.edu
PO Box 137                |
Irvington NY 10533 USA    | http://www.nevis.columbia.edu/~seligman/

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