[Sheepdog] general question about sheepdog operation (block distribution)

[MORITA Kazutaka]

At Mon, 31 Oct 2011 09:07:25 -0000,
Matthew Law wrote:
> 
> On Mon, October 31, 2011 2:17 am, Miles Fidelman wrote:
> > Something that's not quite obvious from the documentation:
> >
> > How does Sheepdog spread blocks around when nodes have multiple disks?
> > For example, on a 4-node cluster, where each node has 4 drives, is
> > Sheepdog smart enough to replicate blocks in ways that protect against
> > both individual drive failures, and node failures that take out 4 drives
> > at a time?
> 
> Hi Miles,
> 
> my understanding of sheepdog is that one would normally run a sheep daemon
> per logical disk.  My testing has been by running a single sheep daemon
> per linux md raid 10 device.  This is obviously overkill but suited my
> setup and sheepdog's features at the time.
> 
> The better solution for current sheepdog is to run one sheep daemon per
> disk and use the failure zones which were recently introduced to tell
> sheepdog 'where' the disks live so it does not place all copies of a block
> of data on a single physical server.

Yes, and Sheepdog uses the same zone id in the same node by default;
dada will be replicated across nodes without any configuration.


Thanks,

Kazutaka