[Sheepdog] Sheepdog reliability

[Dennis Jacobfeuerborn]

Hi,
I've been following Sheepdog for a while and now that patches are being 
sent to include it in libvirt I want to start testing it. One question I 
have is how I can ensure the reliability of the Sheepdog cluster as a 
whole. Specifically I'm looking at two cases:

Lets assume a setup with 4 nodes and a redundancy of 3.

If one node fails what are the effects both for the cluster and the clients 
(e.g. potential i/o delays, messages, etc.) and what needs to be done once 
the node is replaced to get the cluster back into a healthy state?

What happens if *all* nodes fail due to e.g. a power outage? What needs to 
be done to bring the cluster back up again?

Since one of the goals of Sheepdog is to make the storage highly available 
I'm trying to think of the scenarios that the cluster needs to be able to 
handle.

Regards,
   Dennis