[sheepdog-users] Default copies

[Liu Yuan]

On 12/21/2012 07:35 PM, Valerio Pachera wrote:
> I'm just wondering why the default copies are 3 instead of 2.
> 
> Are we able to loose 2 nodes at the same time having 3 copies?
> Other reaon?

Suppose we have 2 copies set,If one node fails, Sheepdog cluster need to
recover the copies on the failed node as soon as possible. In this
*recovery window*, the whole cluster is less reliable because any other
node fails, we'll lose some data which is the only one copy at that time
on the second failed node.

It is a compromiser between data reliability and space efficiency.

Thanks,
Yuan