Osd placement rule questions

[Mark Kirkwood <mark.kirkwood@catalyst.net.nz>]

Hi,

I am experimenting with ceph (rbd only for now), and have a few 
questions about what is possible via placement rules.

For example I am looking at a setup with a local datacenter 
(datacenter0) and a remote one (datacenter1). I'm using a placement rule:

rule rbd {
         ruleset 2
         type replicated
         min_size 1
         max_size 10
         step take datacenter0
         step chooseleaf firstn -1 type host
         step emit
         step take datacenter1
         step chooseleaf firstn 1 type host
         step emit
}

and I have the rdb pool set to size 3.

So I *think* I am saying I want 2 replicas in datacenter0 and one in 
datacenter1 [1].

The questions I have are:

1/ I would like to be able to have a way to say something like: Make 2 
copies at datacenter0, 1 at datacenter1 - wait for the ones at 
datacenter0 to be written but not the ones at datacenter1 (so 
asynchronous for the latter). Is this possible, or planned?

2/ Also I would like to be able to say make my number of copies 3, but 
if I lose datacenter0 (where 2 copies are), don't try to have 3 copies 
at datacenter1 (so run degraded in that case). Is that possible?

Cheers

Mark

[1] Might make more sense to have 2 copies at each, but I'm just trying 
to see how this placement business works at this point...