[sheepdog-users] Several difficulties with sheepdog (from 0.4.0-0+tek2b-10 deb package)

[David Douard]

On 26/08/2012 09:55, Bastian Scholz wrote:
> Hi David,
> 
> Am 2012-07-27 12:02, schrieb David Douard:
>> Done (thanks for the feedback).
> 
> I have rewritten the first part to reflect the zones concept.
> Could you please have a look, if its OK, before change it in
> the wiki?

Done, thanks.


> 
> == General remarks ==
> 
> Sheepdog uses a zone concept for data replication. In the default
> configuration, each node in the cluster is one zone and sheepdog replicate
> the vdi objects to the number of zones defined by the number of copies (X).
> 
> To keep a working cluster, never kill sheeps in more than X-1 zones at
> a time, or during recovery is not finished. If you kill X or more zones
> at a time, you will have no access to some of the objects. It never mind,
> if you kill the complete zone, or only a few sheeps in X different zones
> at a time, there will '''always''' some objects, that are only hold by
> these specific sheeps, only the amount of inaccessible objects will differ.
> 
> Including up to version 0.4 you will '''loose your data''' in this case!
> With the introduction of plain_store and the rework of farm to use it as
> core in version 0.5, you wont loose data, but as long as the zones are not
> restarted, you cant access the objects that are only available on this
> zones and your VM get a I/O Error.
> 
> Thanks Bastian


-- 
--
David DOUARD		LOGILAB
+33 1 45 32 03 12	david.douard at logilab.fr
+33 1 83 64 25 26	http://www.logilab.fr/id/david.douard

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