Some new discovery:
Ubuntu 11.10 is a better OS then Ubuntu 12.04 as an OpenStack host system.
I tried it on Ubuntu 11.10. The volume snapshot can be deleted in very short time. For me, this bug becomes a particular issue for Ubuntu 12.04. Anyway, thank Mike for your concern.
Some new discovery:
Ubuntu 11.10 is a better OS then Ubuntu 12.04 as an OpenStack host system.
I tried it on Ubuntu 11.10. The volume snapshot can be deleted in very short time. For me, this bug becomes a particular issue for Ubuntu 12.04. Anyway, thank Mike for your concern.