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Xen Storage Manager Volume Driver

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Storage Volumes, Disks

Todo

rework after iSCSI merge (see ‘Old Docs’) (todd or vish)

The nova.volume.manager Module

Volume manager manages creating, attaching, detaching, and persistent storage.

Persistant storage volumes keep their state independent of instances. You can attach to an instance, terminate the instance, spawn a new instance (even one from a different image) and re-attach the volume with the same data intact.

Related Flags

volume_topic:What rpc topic to listen to (default: volume).
volume_manager:The module name of a class derived from manager.Manager (default: nova.volume.manager.Manager).
storage_availability_zone:
 Defaults to nova.
volume_driver:Used by Manager. Defaults to nova.volume.driver.ISCSIDriver.
volume_group:Name of the group that will contain exported volumes (default: nova-volumes)
num_shell_tries:
 Number of times to attempt to run commands (default: 3)
class VolumeManager(volume_driver=None, *args, **kwargs)

Bases: nova.manager.SchedulerDependentManager

Manages attachable block storage devices.

VolumeManager.attach_volume(context, volume_id, instance_id, mountpoint)

Updates db to show volume is attached

VolumeManager.check_for_export(context, instance_id)

Make sure whether volume is exported.

VolumeManager.create_snapshot(context, volume_id, snapshot_id)

Creates and exports the snapshot.

VolumeManager.create_volume(context, volume_id, snapshot_id=None)

Creates and exports the volume.

VolumeManager.delete_snapshot(context, snapshot_id)

Deletes and unexports snapshot.

VolumeManager.delete_volume(context, volume_id)

Deletes and unexports volume.

VolumeManager.detach_volume(context, volume_id)

Updates db to show volume is detached

VolumeManager.init_host()

Do any initialization that needs to be run if this is a standalone service.

VolumeManager.initialize_connection(context, volume_id, connector)

Prepare volume for connection from host represented by connector.

This method calls the driver initialize_connection and returns it to the caller. The connector parameter is a dictionary with information about the host that will connect to the volume in the following format:

{
    'ip': ip,
    'initiator': initiator,
}

ip: the ip address of the connecting machine

initiator: the iscsi initiator name of the connecting machine. This can be None if the connecting machine does not support iscsi connections.

driver is responsible for doing any necessary security setup and returning a connection_info dictionary in the following format:

{
    'driver_volume_type': driver_volume_type,
    'data': data,
}
driver_volume_type: a string to identify the type of volume. This
can be used by the calling code to determine the strategy for connecting to the volume. This could be ‘iscsi’, ‘rbd’, ‘sheepdog’, etc.
data: this is the data that the calling code will use to connect
to the volume. Keep in mind that this will be serialized to json in various places, so it should not contain any non-json data types.
VolumeManager.notification(context, event)
VolumeManager.terminate_connection(context, volume_id, connector)

Cleanup connection from host represented by connector.

The format of connector is the same as for initialize_connection.

The nova.volume.driver Module

Drivers for volumes.

class FakeISCSIDriver(*args, **kwargs)

Bases: nova.volume.driver.ISCSIDriver

Logs calls instead of executing.

FakeISCSIDriver.check_for_setup_error()

No setup necessary in fake mode.

static FakeISCSIDriver.fake_execute(cmd, *_args, **_kwargs)

Execute that simply logs the command.

FakeISCSIDriver.initialize_connection(volume, connector)
FakeISCSIDriver.terminate_connection(volume, connector)
class ISCSIDriver(*args, **kwargs)

Bases: nova.volume.driver.VolumeDriver

Executes commands relating to ISCSI volumes.

We make use of model provider properties as follows:

provider_location
if present, contains the iSCSI target information in the same format as an ietadm discovery i.e. ‘<ip>:<port>,<portal> <target IQN>’
provider_auth
if present, contains a space-separated triple: ‘<auth method> <auth username> <auth password>’. CHAP is the only auth_method in use at the moment.
ISCSIDriver.check_for_export(context, volume_id)

Make sure volume is exported.

ISCSIDriver.create_export(context, volume)

Creates an export for a logical volume.

ISCSIDriver.ensure_export(context, volume)

Synchronously recreates an export for a logical volume.

ISCSIDriver.initialize_connection(volume, connector)

Initializes the connection and returns connection info.

The iscsi driver returns a driver_volume_type of ‘iscsi’. The format of the driver data is defined in _get_iscsi_properties. Example return value:

{
    'driver_volume_type': 'iscsi'
    'data': {
        'target_discovered': True,
        'target_iqn': 'iqn.2010-10.org.openstack:volume-00000001',
        'target_portal': '127.0.0.0.1:3260',
        'volume_id': 1,
    }
}
ISCSIDriver.remove_export(context, volume)

Removes an export for a logical volume.

ISCSIDriver.set_execute(execute)
ISCSIDriver.terminate_connection(volume, connector)
class LoggingVolumeDriver(execute=<function execute at 0x96c41ec>, *args, **kwargs)

Bases: nova.volume.driver.VolumeDriver

Logs and records calls, for unit tests.

static LoggingVolumeDriver.all_logs()
LoggingVolumeDriver.check_for_export(context, volume_id)
LoggingVolumeDriver.check_for_setup_error()
static LoggingVolumeDriver.clear_logs()
LoggingVolumeDriver.create_export(context, volume)
LoggingVolumeDriver.create_volume(volume)
LoggingVolumeDriver.delete_volume(volume)
LoggingVolumeDriver.ensure_export(context, volume)
LoggingVolumeDriver.initialize_connection(volume, connector)
LoggingVolumeDriver.local_path(volume)
static LoggingVolumeDriver.log_action(action, parameters)

Logs the command.

static LoggingVolumeDriver.logs_like(action, **kwargs)
LoggingVolumeDriver.remove_export(context, volume)
LoggingVolumeDriver.terminate_connection(volume, connector)
class RBDDriver(execute=<function execute at 0x96c41ec>, *args, **kwargs)

Bases: nova.volume.driver.VolumeDriver

Implements RADOS block device (RBD) volume commands

RBDDriver.check_for_setup_error()

Returns an error if prerequisites aren’t met

RBDDriver.create_export(context, volume)

Exports the volume

RBDDriver.create_snapshot(snapshot)

Creates an rbd snapshot

RBDDriver.create_volume(volume)

Creates a logical volume.

RBDDriver.delete_snapshot(snapshot)

Deletes an rbd snapshot

RBDDriver.delete_volume(volume)

Deletes a logical volume.

RBDDriver.ensure_export(context, volume)

Synchronously recreates an export for a logical volume.

RBDDriver.initialize_connection(volume, connector)
RBDDriver.local_path(volume)

Returns the path of the rbd volume.

RBDDriver.remove_export(context, volume)

Removes an export for a logical volume

RBDDriver.terminate_connection(volume, connector)
class SheepdogDriver(execute=<function execute at 0x96c41ec>, *args, **kwargs)

Bases: nova.volume.driver.VolumeDriver

Executes commands relating to Sheepdog Volumes

SheepdogDriver.check_for_setup_error()

Returns an error if prerequisites aren’t met

SheepdogDriver.create_export(context, volume)

Exports the volume

SheepdogDriver.create_snapshot(snapshot)

Creates a sheepdog snapshot

SheepdogDriver.create_volume(volume)

Creates a sheepdog volume

SheepdogDriver.create_volume_from_snapshot(volume, snapshot)

Creates a sheepdog volume from a snapshot.

SheepdogDriver.delete_snapshot(snapshot)

Deletes a sheepdog snapshot

SheepdogDriver.delete_volume(volume)

Deletes a logical volume

SheepdogDriver.ensure_export(context, volume)

Safely and synchronously recreates an export for a logical volume

SheepdogDriver.initialize_connection(volume, connector)
SheepdogDriver.local_path(volume)
SheepdogDriver.remove_export(context, volume)

Removes an export for a logical volume

SheepdogDriver.terminate_connection(volume, connector)
class VolumeDriver(execute=<function execute at 0x96c41ec>, *args, **kwargs)

Bases: object

Executes commands relating to Volumes.

VolumeDriver.check_for_export(context, volume_id)

Make sure volume is exported.

VolumeDriver.check_for_setup_error()

Returns an error if prerequisites aren’t met

VolumeDriver.create_export(context, volume)

Exports the volume. Can optionally return a Dictionary of changes to the volume object to be persisted.

VolumeDriver.create_snapshot(snapshot)

Creates a snapshot.

VolumeDriver.create_volume(volume)

Creates a logical volume. Can optionally return a Dictionary of changes to the volume object to be persisted.

VolumeDriver.create_volume_from_snapshot(volume, snapshot)

Creates a volume from a snapshot.

VolumeDriver.delete_snapshot(snapshot)

Deletes a snapshot.

VolumeDriver.delete_volume(volume)

Deletes a logical volume.

VolumeDriver.do_setup(context)

Any initialization the volume driver does while starting

VolumeDriver.ensure_export(context, volume)

Synchronously recreates an export for a logical volume.

VolumeDriver.get_volume_stats(refresh=False)

Return the current state of the volume service. If ‘refresh’ is True, run the update first.

VolumeDriver.initialize_connection(volume, connector)

Allow connection to connector and return connection info.

VolumeDriver.local_path(volume)
VolumeDriver.remove_export(context, volume)

Removes an export for a logical volume.

VolumeDriver.set_execute(execute)
VolumeDriver.terminate_connection(volume, connector)

Disallow connection from connector

Tests

The volume_unittest Module

Old Docs

Nova uses ata-over-ethernet (AoE) to export storage volumes from multiple storage nodes. These AoE exports are attached (using libvirt) directly to running instances.

Nova volumes are exported over the primary system VLAN (usually VLAN 1), and not over individual VLANs.

AoE exports are numbered according to a “shelf and blade” syntax. In order to avoid collisions, we currently perform an AoE-discover of existing exports, and then grab the next unused number. (This obviously has race condition problems, and should be replaced by allocating a shelf-id to each storage node.)

The underlying volumes are LVM logical volumes, created on demand within a single large volume group.