openstack/cinder
Code Issues Proposed changes

Dell PowerMax: RDF consistency exempt

Browse Source 
PowerMax allows volumes to be added, removed, or suspended without
affecting the state of the SRDF/A or SRDF/Metro session or requiring
that other volumes in the session be suspended. Known as --exempt for
symcli and editStorageGroupActionParam in the PowerMax REST API,
this capability is available for an SRDF group supporting an active
SRDF/A session or an active SRDF/Metro session.

The PowerMax Cinder driver currently uses the exempt flag when
volumes are added to SRDF groups, but not when volumes are
removed. This incurs an unnecessary performance penalty that is
resolved by this change.

Change-Id: Ic81f2055bae7653226010f0fdfd3aba30897abc1
Signed-off-by: Amit Zauber <amit.zauber@dell.com>
This commit is contained in:
Bryan Neumann
2024-09-03 16:00:21 -04:00
committed by Amit Zauber
parent 8dce75e1d0
commit ad3493c91a
3 changed files with 61 additions and 22 deletions
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12
cinder/tests/unit/volume/drivers/dell_emc/powermax/test_powermax_rest.py
View File

@@ -2084,12 +2084,14 @@ class PowerMaxRestTest(test.TestCase):
rdf_group_no = self.data.rdf_group_no_1
sg_name = self.data.default_sg_re_enabled
rep_extra_specs = self.data.rep_extra_specs
self.rest.srdf_suspend_replication(
array_id, sg_name, rdf_group_no, rep_extra_specs)
# Replication mode in this test is synchronous, so the expecation
# is that the consistency exempt flag is false.
mck_modify.assert_called_once_with(
array_id, rdf_group_no, sg_name,
{'suspend': {'force': 'true'}, 'action': 'Suspend'},
{'suspend': {'force': 'true', 'consExempt': 'false'},
'action': 'Suspend'},
rep_extra_specs, 'Suspend SRDF Group Replication')
@mock.patch.object(rest.PowerMaxRest, 'srdf_modify_group')
@@ -2101,12 +2103,14 @@ class PowerMaxRestTest(test.TestCase):
rdf_group_no = self.data.rdf_group_no_1
sg_name = self.data.default_sg_re_enabled
rep_extra_specs = self.data.rep_extra_specs
self.rest.srdf_suspend_replication(
array_id, sg_name, rdf_group_no, rep_extra_specs)
# Replication mode in this test is synchronous, so the expecation
# is that the consistency exempt flag is false.
mck_modify.assert_called_once_with(
array_id, rdf_group_no, sg_name,
{'suspend': {'force': 'true'}, 'action': 'Suspend'},
{'suspend': {'force': 'true', 'consExempt': 'false'},
'action': 'Suspend'},
rep_extra_specs, 'Suspend SRDF Group Replication')
@mock.patch.object(rest.PowerMaxRest, 'srdf_modify_group')

54
cinder/volume/drivers/dell_emc/powermax/rest.py
View File

@@ -2877,21 +2877,6 @@ class PowerMaxRest(object):
number = None
return number
def _get_async_payload_info(self, array, rdf_group_no):
"""Get the payload details for an async create pair.
:param array: the array serial number
:param rdf_group_no: the rdf group number
:returns: payload_update
"""
num_vols, payload_update = 0, {}
rdfg_details = self.get_rdf_group(array, rdf_group_no)
if rdfg_details is not None and rdfg_details.get('numDevices'):
num_vols = int(rdfg_details['numDevices'])
if num_vols > 0:
payload_update = {'exempt': 'true'}
return payload_update
def get_metro_payload_info(self, array, payload,
rdf_group_no, extra_specs, next_gen):
"""Get the payload details for a metro active create pair.
@@ -2997,15 +2982,48 @@ class PowerMaxRest(object):
if group_state:
group_state = [x.lower() for x in group_state]
if len(group_state) == 1 and utils.RDF_SUSPENDED_STATE in group_state:
LOG.info('SRDF Group %(grp_num)s is already in a suspended state',
{'grp_num': rdf_group_no})
else:
cons_exempt = self._get_cons_exempt(
array_id, storage_group, rdf_group_no,
rep_extra_specs['rep_mode'])
payload = {"suspend": {"force": "true"}, "action": "Suspend"}
payload["suspend"]["consExempt"] = (
"true" if cons_exempt else "false")
self.srdf_modify_group(
array_id, rdf_group_no, storage_group,
{"suspend": {"force": "true"}, "action": "Suspend"},
rep_extra_specs, 'Suspend SRDF Group Replication')
payload, rep_extra_specs,
'Suspend SRDF Group Replication')
def _get_cons_exempt(self, array_id, storage_group, rdf_group_no,
rep_mode=None):
"""Get the consistency exempt flag for a storage group.
:param array_id: array serial number
:param storage_group: storage group name
:param rdf_group_no: RDF group number
:param rep_mode: Replication mode of the SRDF session
:returns: A boolean indicating if consistency is exempt
"""
if not rep_mode:
return False
resource = ('storagegroup/%(sg)s/rdf_group/%(rdfg)s' % {
'sg': storage_group, 'rdfg': rdf_group_no})
rdf_group = self.get_resource(array_id, REPLICATION, resource)
modes = list(rep_mode)
if rdf_group and rdf_group.get('modes'):
modes.append(rdf_group.get('modes'))
# Ensure we don't see the error message:
# "A problem occurred modifying the Storage Group
# SRDF Group resource: The device is not in
# asynchronous mode"
cons_exempt = utils.REP_ASYNC in modes
LOG.debug("Consistency exempt: %s", cons_exempt)
return cons_exempt
def srdf_resume_replication(self, array_id, storage_group, rdf_group_no,
rep_extra_specs, async_call=True):

17
releasenotes/notes/bp-dell-powermax-consistency-exempt.yaml Normal file
View File

@@ -0,0 +1,17 @@
---
features:
- |
Dell PowerMax Driver: use consistency exempt flag consistently
PowerMax allows volumes to be added, removed, or suspended without
affecting the state of the SRDF/A or SRDF/Metro session or requiring
that other volumes in the session be suspended. Known as --exempt for
symcli and editStorageGroupActionParam in the PowerMax REST API,
this capability is available for an SRDF group supporting an active
SRDF/A session or an active SRDF/Metro session.
The PowerMax Cinder driver currently uses the exempt flag when
volumes are added to SRDF groups, but not when volumes are
removed. This incurs an unnecessary performance penalty that is
resolved by this change.
Blueprint: dell-powermax-srdf-exempt