Hi,Following my ideas about using ZFS (ZVol) instead of LVM for the volume (https://lists.launchpad.net/openstack/msg13009.html). I write a piece of code : in attachment or on github/nicolas2bonfils <https://github.com/nicolas2bonfils/cinder/blob/master/cinder/volume/driver_zvol.py> (for line comments or push request). I write and test the code with ZFSOnLinux <http://zfsonlinux.org/> and Debian sid.
What it does : * create ZVol instead of LVM, * use ISCSI sharing from the existing cinder driver, * use ZFS snapshot for the snapshot feature, * is working for create/delete volume, * can create/delete native ZFS snapshot (see below for the linked problem). What need to be improve : * check if native ZFS snapshot can be use for volume snapshot (same use/meaning ?), * when deleting a volume with snapshot (ZFS one), do we delete the derived snapshot or export them as independent volume. What it does not (yet) : * share with native ZFS ISCSI (due to ZFSOnLinux limitation) Thanks for all your ideas, advice, ... --- Nicolas de Bonfils
# vim: tabstop=4 shiftwidth=4 softtabstop=4 # Copyright 2012 Nicolas de Bonfils [email protected] # # Licensed under the Apache License, Version 2.0 (the "License"); you may # not use this file except in compliance with the License. You may obtain # a copy of the License at # # http://www.apache.org/licenses/LICENSE-2.0 # # Unless required by applicable law or agreed to in writing, software # distributed under the License is distributed on an "AS IS" BASIS, WITHOUT # WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the # License for the specific language governing permissions and limitations # under the License. #TODO(nicolas) : i18n the log message from cinder.volume.driver import * class ZVolDriver(ISCSIDriver): """ Drivers for volumes using Zvol instead of LVM. Tested with ZFSOnLinux on a Debian sid system """ def __init__(self, *args, **kwargs): #TODO(nicolas) : use configuration flag self.zfs_bin = "/sbin/zfs" self.zpool_bin = "/sbin/zpool" super(ZVolDriver, self).__init__(*args, **kwargs) def check_for_setup_error(self): """Returns an error if prerequisites aren't met""" out, err = self._execute('%s' % self.zfs_bin, 'list', run_as_root=True) volume_groups = out.split() if not FLAGS.volume_group in volume_groups: raise exception.Error(_("zfs base volume group '%s' doesn't exist") % FLAGS.volume_group) def _create_volume(self, volume_name, sizestr): LOG.debug('Create volume with command "%s create -V %s %s/%s"' % (self.zfs_bin, sizestr, FLAGS.volume_group, volume_name)) self._try_execute('%s' % self.zfs_bin, 'create', '-V', sizestr, '%s/%s' % (FLAGS.volume_group, volume_name), run_as_root=True) def _copy_volume(self, srcstr, deststr, size_in_g): LOG.debug('copy volume with method "dd if=%s of=%s count=%d bs=1M"' % (srcstr, deststr, (size_in_g * 1024))) self._execute('dd', 'if=%s' % srcstr, 'of=%s' % deststr, 'count=%d' % (size_in_g * 1024), 'bs=1M', run_as_root=True) def _volume_not_present(self, volume_name): path_name = '%s/%s' % (FLAGS.volume_group, volume_name) out, err = self._execute('%s' % self.zfs_bin, 'list', run_as_root=True) volume_search = out.split() LOG.debug('List volume with command "%s list"' % self.zfs_bin) LOG.debug(volume_search) return not path_name in volume_search def _delete_volume(self, volume, size_in_g): """Deletes a zvol.""" # zero out old volumes to prevent data leaking between users # TODO(ja): reclaiming space should be done lazy and low priority self._copy_volume('/dev/zero', self.local_path(volume), size_in_g) LOG.debug('Destroy volume with command "%s destroy %s/%s"' % (self.zfs_bin, FLAGS.volume_group, volume['name'])) self._try_execute('%s' % self.zfs_bin, 'destroy', '%s/%s' % (FLAGS.volume_group, volume['name']), run_as_root=True) def delete_volume(self, volume): """Deletes a zvol.""" if self._volume_not_present(volume['name']): # If the volume isn't present, then don't attempt to delete return True # When snapshots exist, what to do ? # remove them or export them as new independent volume self._delete_volume(volume, volume['size']) def create_snapshot(self, snapshot): """Creates a snapshot.""" LOG.debug('Snapshot volume with command "%s snapshot %s/%s"' % (self.zfs_bin, FLAGS.volume_group, self._snapshot_full_name(snapshot))) self._try_execute('%s' % self.zfs_bin, 'snapshot', '%s/%s' % (FLAGS.volume_group, self._snapshot_full_name(snapshot)), run_as_root=True) def delete_snapshot(self, snapshot): """Deletes a snapshot.""" if self._volume_not_present(self._snapshot_full_name(snapshot)): # If the snapshot isn't present, then don't attempt to delete return True self._delete_volume(snapshot, snapshot['volume_size']) def local_path(self, volume): """Give full path to the system /dev object""" full_name = "" # if we got a volume name, then it's a snapshot so create the full path # otherwise it a "regular" volume # it's a hack to know if volume "respond to" volume_name key. #FIXME(nicolas) : volume is sqlalchemy object, how to query existence for a property/method ? try: volume_name = volume['volume_name'] full_name = self._snapshot_full_name(volume) except Exception as e: full_name = volume['name'] return "/dev/zvol/%s/%s" % (FLAGS.volume_group, full_name) def _snapshot_full_name(self, snapshot): """Give the snapshot full name : volume name + snapshot name with '@' in the middle """ return '%s@%s' % (snapshot['volume_name'], snapshot['name'])
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