Volume tests fail if volume sizes are set to round off like in ScaleIO based cinder-backend deployments

[Imran Hayder]

OVERVIEW:
We are running tempest latest against newton based deployment.
Our cinder backend is EMC ScaleIO where the volume size is rounded off to nearest integer which is multiple original volume size.
So if CONF.volume.volume_size is set to 8, CONF.volume.volume_size + 1 = 16 in ScaleIO based backends because 16 is nearest multiple of 8 and scaleIO rounds off to 16 instead of 9.
this makes certain snapshots fail like :

tempest.api.volume.test_volumes_snapshots.VolumesV2SnapshotTestJSON.test_volume_from_snapshot[id-677863d1-3142-456d-b6ac-9924f667a7f4]

Stacktrace

Traceback (most recent call last):
testtools.testresult.real._StringException: Empty attachments:
  pythonlogging:''
  stderr
  stdout

Traceback (most recent call last):
  File "tempest/api/volume/test_volumes_snapshots.py", line 122, in test_volume_from_snapshot
    self.assertEqual(int(volume['size']), src_size + 1)
  File "/var/lib/jenkins/workspace/refstack_cloud_compute/refstack-client/.tempest/.venv/lib/python2.7/site-packages/testtools/testcase.py", line 411, in assertEqual
    self.assertThat(observed, matcher, message)
  File "/var/lib/jenkins/workspace/refstack_cloud_compute/refstack-client/.tempest/.venv/lib/python2.7/site-packages/testtools/testcase.py", line 498, in assertThat
    raise mismatch_error
testtools.matchers._impl.MismatchError: 16 != 9

Please add option for round off of volume size increment.

[Imran Hayder (hayderimran7)]

I found out that volume increment by 1 check was recently added in tempest(tags 13.0.0 and 12.0.0 ) which breaks this test for us https://github.com/openstack/tempest/commit/8dbbc297b460347451929abf611ef05d6ac56f4b
using older version of tempest(like tag 10.0.0) we have this test passing

[Jordan Pittier (jordan-pittier)]

"So if CONF.volume.volume_size is set to 8, CONF.volume.volume_size + 1 = 16 in ScaleIO based backends because 16 is nearest multiple of 8 and scaleIO rounds off to 16 instead of 9."

That sounds crazy. If I ask for a 9G volume, I want a 9G volume. Tempest should check for a 9G volume. That's how it is. Either report your request to EMC or Cinder.