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diff --git a/doc/rbd/rbd-openstack.rst b/doc/rbd/rbd-openstack.rst new file mode 100644 index 000000000..3f1b85f30 --- /dev/null +++ b/doc/rbd/rbd-openstack.rst @@ -0,0 +1,395 @@ +============================= + Block Devices and OpenStack +============================= + +.. index:: Ceph Block Device; OpenStack + +You can attach Ceph Block Device images to OpenStack instances through ``libvirt``, +which configures the QEMU interface to ``librbd``. Ceph stripes block volumes +across multiple OSDs within the cluster, which means that large volumes can +realize better performance than local drives on a standalone server! + +To use Ceph Block Devices with OpenStack, you must install QEMU, ``libvirt``, +and OpenStack first. We recommend using a separate physical node for your +OpenStack installation. OpenStack recommends a minimum of 8GB of RAM and a +quad-core processor. The following diagram depicts the OpenStack/Ceph +technology stack. + + +.. ditaa:: + + +---------------------------------------------------+ + | OpenStack | + +---------------------------------------------------+ + | libvirt | + +------------------------+--------------------------+ + | + | configures + v + +---------------------------------------------------+ + | QEMU | + +---------------------------------------------------+ + | librbd | + +---------------------------------------------------+ + | librados | + +------------------------+-+------------------------+ + | OSDs | | Monitors | + +------------------------+ +------------------------+ + +.. important:: To use Ceph Block Devices with OpenStack, you must have + access to a running Ceph Storage Cluster. + +Three parts of OpenStack integrate with Ceph's block devices: + +- **Images**: OpenStack Glance manages images for VMs. Images are immutable. + OpenStack treats images as binary blobs and downloads them accordingly. + +- **Volumes**: Volumes are block devices. OpenStack uses volumes to boot VMs, + or to attach volumes to running VMs. OpenStack manages volumes using + Cinder services. + +- **Guest Disks**: Guest disks are guest operating system disks. By default, + when you boot a virtual machine, its disk appears as a file on the file system + of the hypervisor (usually under ``/var/lib/nova/instances/<uuid>/``). Prior + to OpenStack Havana, the only way to boot a VM in Ceph was to use the + boot-from-volume functionality of Cinder. However, now it is possible to boot + every virtual machine inside Ceph directly without using Cinder, which is + advantageous because it allows you to perform maintenance operations easily + with the live-migration process. Additionally, if your hypervisor dies it is + also convenient to trigger ``nova evacuate`` and reinstate the virtual machine + elsewhere almost seamlessly. In doing so, + :ref:`exclusive locks <rbd-exclusive-locks>` prevent multiple + compute nodes from concurrently accessing the guest disk. + + +You can use OpenStack Glance to store images as Ceph Block Devices, and you +can use Cinder to boot a VM using a copy-on-write clone of an image. + +The instructions below detail the setup for Glance, Cinder and Nova, although +they do not have to be used together. You may store images in Ceph block devices +while running VMs using a local disk, or vice versa. + +.. important:: Using QCOW2 for hosting a virtual machine disk is NOT recommended. + If you want to boot virtual machines in Ceph (ephemeral backend or boot + from volume), please use the ``raw`` image format within Glance. + +.. index:: pools; OpenStack + +Create a Pool +============= + +By default, Ceph block devices live within the ``rbd`` pool. You may use any +suitable pool by specifying it explicitly. We recommend creating a pool for +Cinder and a pool for Glance. Ensure your Ceph cluster is running, then create the pools. :: + + ceph osd pool create volumes + ceph osd pool create images + ceph osd pool create backups + ceph osd pool create vms + +See `Create a Pool`_ for detail on specifying the number of placement groups for +your pools, and `Placement Groups`_ for details on the number of placement +groups you should set for your pools. + +Newly created pools must be initialized prior to use. Use the ``rbd`` tool +to initialize the pools:: + + rbd pool init volumes + rbd pool init images + rbd pool init backups + rbd pool init vms + +.. _Create a Pool: ../../rados/operations/pools#createpool +.. _Placement Groups: ../../rados/operations/placement-groups + + +Configure OpenStack Ceph Clients +================================ + +The nodes running ``glance-api``, ``cinder-volume``, ``nova-compute`` and +``cinder-backup`` act as Ceph clients. Each requires the ``ceph.conf`` file:: + + ssh {your-openstack-server} sudo tee /etc/ceph/ceph.conf </etc/ceph/ceph.conf + + +Install Ceph client packages +---------------------------- + +On the ``glance-api`` node, you will need the Python bindings for ``librbd``:: + + sudo apt-get install python-rbd + sudo yum install python-rbd + +On the ``nova-compute``, ``cinder-backup`` and on the ``cinder-volume`` node, +use both the Python bindings and the client command line tools:: + + sudo apt-get install ceph-common + sudo yum install ceph-common + + +Setup Ceph Client Authentication +-------------------------------- + +If you have `cephx authentication`_ enabled, create a new user for Nova/Cinder +and Glance. Execute the following:: + + ceph auth get-or-create client.glance mon 'profile rbd' osd 'profile rbd pool=images' mgr 'profile rbd pool=images' + ceph auth get-or-create client.cinder mon 'profile rbd' osd 'profile rbd pool=volumes, profile rbd pool=vms, profile rbd-read-only pool=images' mgr 'profile rbd pool=volumes, profile rbd pool=vms' + ceph auth get-or-create client.cinder-backup mon 'profile rbd' osd 'profile rbd pool=backups' mgr 'profile rbd pool=backups' + +Add the keyrings for ``client.cinder``, ``client.glance``, and +``client.cinder-backup`` to the appropriate nodes and change their ownership:: + + ceph auth get-or-create client.glance | ssh {your-glance-api-server} sudo tee /etc/ceph/ceph.client.glance.keyring + ssh {your-glance-api-server} sudo chown glance:glance /etc/ceph/ceph.client.glance.keyring + ceph auth get-or-create client.cinder | ssh {your-volume-server} sudo tee /etc/ceph/ceph.client.cinder.keyring + ssh {your-cinder-volume-server} sudo chown cinder:cinder /etc/ceph/ceph.client.cinder.keyring + ceph auth get-or-create client.cinder-backup | ssh {your-cinder-backup-server} sudo tee /etc/ceph/ceph.client.cinder-backup.keyring + ssh {your-cinder-backup-server} sudo chown cinder:cinder /etc/ceph/ceph.client.cinder-backup.keyring + +Nodes running ``nova-compute`` need the keyring file for the ``nova-compute`` +process:: + + ceph auth get-or-create client.cinder | ssh {your-nova-compute-server} sudo tee /etc/ceph/ceph.client.cinder.keyring + +They also need to store the secret key of the ``client.cinder`` user in +``libvirt``. The libvirt process needs it to access the cluster while attaching +a block device from Cinder. + +Create a temporary copy of the secret key on the nodes running +``nova-compute``:: + + ceph auth get-key client.cinder | ssh {your-compute-node} tee client.cinder.key + +Then, on the compute nodes, add the secret key to ``libvirt`` and remove the +temporary copy of the key:: + + uuidgen + 457eb676-33da-42ec-9a8c-9293d545c337 + + cat > secret.xml <<EOF + <secret ephemeral='no' private='no'> + <uuid>457eb676-33da-42ec-9a8c-9293d545c337</uuid> + <usage type='ceph'> + <name>client.cinder secret</name> + </usage> + </secret> + EOF + sudo virsh secret-define --file secret.xml + Secret 457eb676-33da-42ec-9a8c-9293d545c337 created + sudo virsh secret-set-value --secret 457eb676-33da-42ec-9a8c-9293d545c337 --base64 $(cat client.cinder.key) && rm client.cinder.key secret.xml + +Save the uuid of the secret for configuring ``nova-compute`` later. + +.. important:: You don't necessarily need the UUID on all the compute nodes. + However from a platform consistency perspective, it's better to keep the + same UUID. + +.. _cephx authentication: ../../rados/configuration/auth-config-ref/#enabling-disabling-cephx + + +Configure OpenStack to use Ceph +=============================== + +Configuring Glance +------------------ + +Glance can use multiple back ends to store images. To use Ceph block devices by +default, configure Glance like the following. + + +Kilo and after +~~~~~~~~~~~~~~ + +Edit ``/etc/glance/glance-api.conf`` and add under the ``[glance_store]`` section:: + + [glance_store] + stores = rbd + default_store = rbd + rbd_store_pool = images + rbd_store_user = glance + rbd_store_ceph_conf = /etc/ceph/ceph.conf + rbd_store_chunk_size = 8 + +For more information about the configuration options available in Glance please refer to the OpenStack Configuration Reference: http://docs.openstack.org/. + +Enable copy-on-write cloning of images +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +Note that this exposes the back end location via Glance's API, so the endpoint +with this option enabled should not be publicly accessible. + +Any OpenStack version except Mitaka +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +If you want to enable copy-on-write cloning of images, also add under the ``[DEFAULT]`` section:: + + show_image_direct_url = True + +Disable cache management (any OpenStack version) +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +Disable the Glance cache management to avoid images getting cached under ``/var/lib/glance/image-cache/``, +assuming your configuration file has ``flavor = keystone+cachemanagement``:: + + [paste_deploy] + flavor = keystone + +Image properties +~~~~~~~~~~~~~~~~ + +We recommend to use the following properties for your images: + +- ``hw_scsi_model=virtio-scsi``: add the virtio-scsi controller and get better performance and support for discard operation +- ``hw_disk_bus=scsi``: connect every cinder block devices to that controller +- ``hw_qemu_guest_agent=yes``: enable the QEMU guest agent +- ``os_require_quiesce=yes``: send fs-freeze/thaw calls through the QEMU guest agent + + +Configuring Cinder +------------------ + +OpenStack requires a driver to interact with Ceph block devices. You must also +specify the pool name for the block device. On your OpenStack node, edit +``/etc/cinder/cinder.conf`` by adding:: + + [DEFAULT] + ... + enabled_backends = ceph + glance_api_version = 2 + ... + [ceph] + volume_driver = cinder.volume.drivers.rbd.RBDDriver + volume_backend_name = ceph + rbd_pool = volumes + rbd_ceph_conf = /etc/ceph/ceph.conf + rbd_flatten_volume_from_snapshot = false + rbd_max_clone_depth = 5 + rbd_store_chunk_size = 4 + rados_connect_timeout = -1 + +If you are using `cephx authentication`_, also configure the user and uuid of +the secret you added to ``libvirt`` as documented earlier:: + + [ceph] + ... + rbd_user = cinder + rbd_secret_uuid = 457eb676-33da-42ec-9a8c-9293d545c337 + +Note that if you are configuring multiple cinder back ends, +``glance_api_version = 2`` must be in the ``[DEFAULT]`` section. + + +Configuring Cinder Backup +------------------------- + +OpenStack Cinder Backup requires a specific daemon so don't forget to install it. +On your Cinder Backup node, edit ``/etc/cinder/cinder.conf`` and add:: + + backup_driver = cinder.backup.drivers.ceph + backup_ceph_conf = /etc/ceph/ceph.conf + backup_ceph_user = cinder-backup + backup_ceph_chunk_size = 134217728 + backup_ceph_pool = backups + backup_ceph_stripe_unit = 0 + backup_ceph_stripe_count = 0 + restore_discard_excess_bytes = true + + +Configuring Nova to attach Ceph RBD block device +------------------------------------------------ + +In order to attach Cinder devices (either normal block or by issuing a boot +from volume), you must tell Nova (and libvirt) which user and UUID to refer to +when attaching the device. libvirt will refer to this user when connecting and +authenticating with the Ceph cluster. :: + + [libvirt] + ... + rbd_user = cinder + rbd_secret_uuid = 457eb676-33da-42ec-9a8c-9293d545c337 + +These two flags are also used by the Nova ephemeral back end. + + +Configuring Nova +---------------- + +In order to boot virtual machines directly from Ceph volumes, you must +configure the ephemeral backend for Nova. + +It is recommended to enable the RBD cache in your Ceph configuration file; this +has been enabled by default since the Giant release. Moreover, enabling the +client admin socket allows the collection of metrics and can be invaluable +for troubleshooting. + +This socket can be accessed on the hypvervisor (Nova compute) node:: + + ceph daemon /var/run/ceph/ceph-client.cinder.19195.32310016.asok help + +To enable RBD cache and admin sockets, ensure that on each hypervisor's +``ceph.conf`` contains:: + + [client] + rbd cache = true + rbd cache writethrough until flush = true + admin socket = /var/run/ceph/guests/$cluster-$type.$id.$pid.$cctid.asok + log file = /var/log/qemu/qemu-guest-$pid.log + rbd concurrent management ops = 20 + +Configure permissions for these directories:: + + mkdir -p /var/run/ceph/guests/ /var/log/qemu/ + chown qemu:libvirtd /var/run/ceph/guests /var/log/qemu/ + +Note that user ``qemu`` and group ``libvirtd`` can vary depending on your system. +The provided example works for RedHat based systems. + +.. tip:: If your virtual machine is already running you can simply restart it to enable the admin socket + + +Restart OpenStack +================= + +To activate the Ceph block device driver and load the block device pool name +into the configuration, you must restart the related OpenStack services. +For Debian based systems execute these commands on the appropriate nodes:: + + sudo glance-control api restart + sudo service nova-compute restart + sudo service cinder-volume restart + sudo service cinder-backup restart + +For Red Hat based systems execute:: + + sudo service openstack-glance-api restart + sudo service openstack-nova-compute restart + sudo service openstack-cinder-volume restart + sudo service openstack-cinder-backup restart + +Once OpenStack is up and running, you should be able to create a volume +and boot from it. + + +Booting from a Block Device +=========================== + +You can create a volume from an image using the Cinder command line tool:: + + cinder create --image-id {id of image} --display-name {name of volume} {size of volume} + +You can use `qemu-img`_ to convert from one format to another. For example:: + + qemu-img convert -f {source-format} -O {output-format} {source-filename} {output-filename} + qemu-img convert -f qcow2 -O raw precise-cloudimg.img precise-cloudimg.raw + +When Glance and Cinder are both using Ceph block devices, the image is a +copy-on-write clone, so new volumes are created quickly. In the OpenStack +dashboard, you can boot from that volume by performing the following steps: + +#. Launch a new instance. +#. Choose the image associated to the copy-on-write clone. +#. Select 'boot from volume'. +#. Select the volume you created. + +.. _qemu-img: ../qemu-rbd/#running-qemu-with-rbd |