[sheepdog] read/write during recovery

[Dietmar Maurer]

> > How do you detect the point in time when it is safe to remove an
> > object (because all new members have all data the need)?
> 
> Sorry, I'm afraid I don't understand the question.  Which objects do we need
> to remove?  Can you give an example?

When we re-balance. For example

1.) obj is store on Nodes A and B
2.) we add new node C, which changes obj mapping to B and C
3.) C recovers, and copies obj data
4.) We can now remove obj from Node A