Ceph

While it's probably the case that the various tools should disallow setting pool size to 0, currently it's possible; however, if you do so, bad things happen. I think it caused the osd's to both die, but it certainly prevents them from starting up with a segv in

0x000000000123d782 in pg_interval_t::check_new_interval (
    old_acting=std::vector of length 0, capacity 0, 
    new_acting=std::vector of length 2, capacity 2 = {...}, 
    old_up=std::vector of length 0, capacity 0, 
    new_up=std::vector of length 2, capacity 2 = {...}, 
    same_interval_since=377, last_epoch_clean=375, osdmap=
    std::tr1::shared_ptr (count 13, weak 1) 0x20d2b60, 
    lastmap=std::tr1::shared_ptr (count 1033, weak 1) 0x20d2680, pool_id=2, 
    pgid=..., past_intervals=0x2976130, out=0x0) at osd/osd_types.cc:1602

I suspect there are some places that a "if !v.empty()" should be added.