Hi all. 
we 'd like to explore storage back end alternatives to CEPH for Openstack 

I am aware of GlusterFS but what would you recommend for distributed storage like Ceph and specifically for block device provisioning? 
Of course must be:
  1. Reliable
  2. Fast
  3. Capable of good performance over WAN given a good network back end
Both open source and commercial technologies and ideas are welcome.

Cheers

--
Alfredo