Problem

This error may 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 <iSCSI Qualified Name
(IQN)> if the host was exported using iSCSI:

Duplicate3PARHost: 3PAR Host already exists: Host wwn 50014380242B9750 \
already used by host cld4b5ubuntuW(id = 68. The hostname must be called\
'cld4b5ubuntu'.

Solution

Change the 3PAR host name to match the one that OpenStack expects.
The 3PAR host constructed by the driver uses 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.