Description of problem:
In virtual environment , i have emulated root disk as scsi disk & 7 other disks as virtio on ceph nodes .
Introspection fails for ceph nodes with following error .
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Dec 08 21:33:24 host-192-0-2-12 ironic-python-agent[390]: 2016-12-08 21:33:24.831 390 ERROR root [-] Unexpected error dispatching get_os_install_device to manager <ironic_python_agent.hardware.GenericHardwareManager object at 0x307d090>: Error finding the disk or partition device to deploy the image onto: No suitable device was found for deployment using these hints {u'vendor': u'ATA'}
Dec 08 21:33:24 host-192-0-2-12 ironic-python-agent[390]: 2016-12-08 21:33:24.831 390 ERROR root Traceback (most recent call last):
Dec 08 21:33:24 host-192-0-2-12 ironic-python-agent[390]: 2016-12-08 21:33:24.831 390 ERROR root   File "/usr/lib/python2.7/site-packages/ironic_python_agent/hardware.py", line 1062, in dispatch_to_managers
Dec 08 21:33:24 host-192-0-2-12 ironic-python-agent[390]: 2016-12-08 21:33:24.831 390 ERROR root     return getattr(manager, method)(*args, **kwargs)
Dec 08 21:33:24 host-192-0-2-12 ironic-python-agent[390]: 2016-12-08 21:33:24.831 390 ERROR root   File "/usr/lib/python2.7/site-packages/ironic_python_agent/hardware.py", line 688, in get_os_install_device
Dec 08 21:33:24 host-192-0-2-12 ironic-python-agent[390]: 2016-12-08 21:33:24.831 390 ERROR root     "deployment using these hints %s" % root_device_hints)
Dec 08 21:33:24 host-192-0-2-12 ironic-python-agent[390]: 2016-12-08 21:33:24.831 390 ERROR root DeviceNotFound: Error finding the disk or partition device to deploy the image onto: No suitable device was found for deployment using these hints {u'vendor': u'ATA'}
Dec 08 21:33:24 host-192-0-2-12 ironic-python-agent[390]: 2016-12-08 21:33:24.831 390 ERROR root
Dec 08 21:33:24 host-192-0-2-12 ironic-python-agent[390]: 2016-12-08 21:33:24.833 390 ERROR root [-] Command execution error: Error finding the disk or partition device to deploy the image onto: No suitable device was found for deployment using these hints {u'vendor': u'ATA'}
Dec 08 21:33:24 host-192-0-2-12 ironic-python-agent[390]: 2016-12-08 21:33:24.833 390 ERROR root Traceback (most recent call last):
Dec 08 21:33:24 host-192-0-2-12 ironic-python-agent[390]: 2016-12-08 21:33:24.833 390 ERROR root   File "/usr/lib/python2.7/site-packages/ironic_python_agent/extensions/base.py", line 251, in execute_command
Dec 08 21:33:24 host-192-0-2-12 ironic-python-agent[390]: 2016-12-08 21:33:24.833 390 ERROR root     result = ext.execute(command_part, **kwargs)

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This failure is only seen for 'vendor / model / size' & not for name .
The config known to fail :
   55  for i in `cat ceph.txt`; do ironic node-update $i replace properties/root_device='{"vendor":"ATA"}' ; done
   68  for i in `cat ceph.txt`; do ironic node-update $i replace properties/root_device='{"model":"QEMU HARDDISK"}' ; done
   96  for i in `cat ceph.txt`; do ironic node-update $i replace properties/root_device='{"size":"44"}' ; done
The config known to work :
   86  for i in `cat ceph.txt`; do ironic node-update $i replace properties/root_device='{"name":"/dev/sda"}' ; done

Version-Release number of selected component (if applicable):
2016-11-10.3

How reproducible:
Always on virtual environment deployed via instack-virt-setup .
Not on baremetal ironic nodes .

Steps to Reproduce:
1. Deploy virtual env with instack-virt-setup .
2. Add one or more disk to one vm .
3. deploy undercloud + images .
4. introspect the node. 
5. check data in introspected data & set root hints with either 'vendor / model / size'  .

Actual results:
Introspection fails.

Expected results:
Introspection should work if the data matches the 'vendor / model / size' for previous introspection data .

Additional info:
PFA logs . 
I am not quite sure if this is a bug , but this is a part of script that i used for RHOS7/8/9 & it worked well on virtual environments .
I tested on baremetal using vendor root hint but that worked .