[Sheepdog] Option 'copies'

[MORITA Kazutaka]

At Sat, 20 Aug 2011 16:22:17 +0200,
Valerio Pachera wrote:
> 
> From getting started:
> 'It is enough to run this command on one of machines. "--copies"
> specifies the number of default data redundancy. In this case, the
> replicated data will be stored on three machines.'
> 
> Correct me if I'm wrong: using --copies=3, I have always at least 3
> copies for any chunck of a vdi disk.
> So, if my scluster uses 5 or more nodes, when one of them dies, the
> chunks stored on will be moved to the other nodes.

Yes.

> 
> The chunks are distrubted  on all nodes. So I do not have 3 nodes with
> data and 2 without.
> 
> If I add a node (the 6th) simply by "sheep /speed_data", the chinks
> will automatically be distrbuted also on the new node.

Yes.

> 
> If I shutdown a node after the other, giving it the time necessesary
> for data sync, all the data will be move to the last node (off course
> with enough space).
> There will be no redudance and the last node will not have any 'extra'
> chunk copy left.

As you may know, you should run "collie cluster shutdown" before
stopping a Sheepdog cluster to avoid extra data copies..

> 
> In this schenario, one node "exports" one directory, so removing a
> node equals to remve a "cluster member". Anyway, a single node can
> export more directories so ti would be more correct to speak about
> "removing directory form the cluster"?

I'm not sure this answers your questions, but currently you need to
run multiple sheep daemons to handle multiple directories.


Thanks,

Kazutaka