This error could be caused by a volume being exported outside of OpenStack using a host name different from the system name that OpenStack expects. This error could be displayed with the IQN if the host was exported using iSCSI.
2013-04-19 04:02:02.336 2814 ERROR cinder.openstack.common.rpc.common [-] Returning exception Not found (HTTP 404) NON_EXISTENT_HOST - HOST '10' was not found to caller.
Host names constructed by the driver use just the local host name, not the fully qualified domain name (FQDN) of the Compute host. For example, if the FQDN was myhost.example.com, just myhost would be used as the 3PAR host name. IP addresses are not allowed as host names on the 3PAR storage server.