[pve-devel] question about pve-qemu && librbd

[Fabian Grünbichler]

On Mon, Sep 25, 2017 at 03:10:11PM +0200, Alexandre DERUMIER wrote:
> >>there might be some yet undiscovered incompatibility when mixing versions like
> >>that (there are other ceph libraries with reverse-dependencies to
> >>consider as well)
> 
> But proxmox 5.0 ceph-server only support luminous, right ?
> so, I think it shouldn't be a problem ?

yes, as hyper-converged setup using pveceph we only support Luminous.

but for other use cases, we don't (yet?) have that limitation. e.g.,
running a radosgw (which is a client from Ceph's perspective) or just
rbd access to an external cluster is supported using Jewel as well.

> and from client side, librbd is backward compatible to connect on older cluster (I have tested lirbd luminous to jewel && hammer cluster without any problem)
> 

if we move librbd1, we'd have to move ceph-common, which means we'd have
to move ceph-base, ceph-osd, ceph-mon and ceph, as well as radosgw and
end up with a horrible mix of package versions which is most likely not
tested by anyone else.

so these are the options:
- merge ceph and regular PVE repos (not possible to support multiple
  Ceph versions in the future!)
- keep everything as is, losing a bit of performance
- patch Qemu to do runtime loading and feature detection for librbd
- build a second qemu package linked with librbd1 from Ceph repo and put
  it in Ceph repo (either with higher version, or with different package
  name and provides+replaces)