[pve-devel] Two-Node HA

[Michael Rasmussen]

If you search the forum you will find a step guide for using a rpi as third node.

On September 28, 2016 5:53:05 PM GMT+02:00, Andreas Steinel <a.steinel at gmail.com> wrote:
>Hi Thomas,
>
>Thank you for your time and your answer.
>
>I wonder why e.g. an Oracle Real Application Cluster (RAC) works so
>well with a 2 node in a HA setup. We deployed 50+ clusters in the last
>years and never had a split-brain-like situation. Rolling-updates, as
>well as occasional host crashes are also possible without loosing data
>- sometimes even sessions. If you use Transparent Failover (TAF), your
>database sessions will be migrated to the other node, rolled back and
>restarted (of course application support required on the "client"
>side). It's not perfect, but most of the time. We had only a few total
>crashes, but mainly due to storage issues, but also due to some bugs
>in the cluster stack.
>
>Nevertheless, it's very good to see that a simple third vote solution
>is on the horizon, which could be easily integrated in a RPi or an
>even less "powerhungry" machine.
>
>Best,
>Andreas
>
>On Wed, Sep 28, 2016 at 3:46 PM, Thomas Lamprecht
><t.lamprecht at proxmox.com> wrote:
>> Hi,
>>
>> QDisks are not ideal and those itself will probably not supported by
>Proxmox
>> VE, also I would really love top see the term "two node HA" vanish,
>as its
>> only marketing talk and is technically simply not possible (sadly
>basic
>> rules of our universe make it impossible), they call a setup with
>three
>> voters (the two nodes + the storage node) two node HA to sound
>better...
>>
>> That said, rant aside, there are plans to add the corosync (our
>cluster
>> communication stack) QDevice daemon which allows then qdevices (at
>the
>> moment there is only QNetd) to provide votes for one or more cluster.
>>
>> This QNetd device may run on a non Proxmox VE node and uses TCP/IP to
>> communicate with the cluster.
>>
>> So you can have a two node cluster, setup the qdevice daemon there
>and the
>> qnetd daemon on your storage box which then provides the third vote
>needed
>> to allow recovery on a failure of one of the two Proxmox VE nodes.
>>
>> Patches for this are already on the list, whats mainly missing is -
>> obviously - reviewing them and documentation of this all (which I'm
>doing
>> atm).
>>
>> cheers,
>> Thomas
>>
>>
>>
>> On 09/28/2016 03:26 PM, Andreas Steinel wrote:
>>>
>>> Hi,
>>>
>>> I'd like to ask if there are any plans to use e.g. the shared
>storage
>>> as a quorum/voting disk like the oracle grid infrastructure uses it
>to
>>> get a two node ha cluster (for almost a decade). This obviously only
>>> works for NAS or SAN storage.
>>>
>>> Best,
>>> Andreas
>>> _______________________________________________
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>>> pve-devel at pve.proxmox.com
>>> http://pve.proxmox.com/cgi-bin/mailman/listinfo/pve-devel
>>
>>
>>
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