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

[Bastian Scholz]

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?

== 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