bd3b00a532
The Block Storage Section, originally written for libcloud now has support for other SDKs. libcloud should be treated the same as other SDKs, so this patch simply moves the code samples into a dedicated file, as per the per all other sections. Change-Id: Ide9e8f29aec37b0410d133549679406ecdc0cce2
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9.1 KiB
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310 lines
9.1 KiB
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=============
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Block Storage
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=============
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.. todo:: (For nick: Restructure the introduction to this chapter to
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provide context of what we're actually going to do.)
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By default, data in OpenStack instances is stored on 'ephemeral'
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disks. These disks remain with the instance throughout its lifetime.
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When you terminate the instance, that storage and all the data stored
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on it disappears. Ephemeral storage is allocated to a single instance
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and cannot be moved to another instance.
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This section introduces block storage, also known as volume storage,
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which provides access to persistent storage devices. You interact with
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block storage by attaching volumes to running instances just as you
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might attach a USB drive to a physical server. You can detach volumes
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from one instance and reattach them to another instance and the data
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remains intact. The OpenStack Block Storage (cinder) project
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implements block storage.
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Though you might have configured Object Storage to store images, the
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Fractal application needs a database to track the location of, and
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parameters that were used to create, images in Object Storage. This
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database server cannot fail.
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If you are an advanced user, think about how you might remove the
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database from the architecture and replace it with Object Storage
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metadata, and then contribute these steps to :doc:`craziness`.
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Otherwise, continue reading to learn how to work with, and move the
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Fractal application database server to use, block storage.
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Basics
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~~~~~~
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Later on, you will use a Block Storage volume to provide persistent
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storage for the database server for the Fractal application. But
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first, learn how to create and attach a Block Storage device.
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.. only:: dotnet
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.. warning:: This section has not yet been completed for the .NET SDK.
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.. only:: fog
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.. warning:: This section has not yet been completed for the fog SDK.
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.. only:: jclouds
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.. warning:: This section has not yet been completed for the jclouds SDK.
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.. only:: pkgcloud
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.. warning:: This section has not yet been completed for the pkgcloud SDK.
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.. only:: openstacksdk
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.. warning:: This section has not yet been completed for the OpenStack SDK.
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.. only:: phpopencloud
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.. warning:: This section has not yet been completed for the
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PHP-OpenCloud SDK.
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Connect to the API endpoint:
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.. only:: libcloud
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.. literalinclude:: ../samples/libcloud/block_storage.py
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:language: python
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:start-after: step-1
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:end-before: step-2
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.. only:: shade
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.. literalinclude:: ../samples/shade/block_storage.py
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:language: python
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:start-after: step-1
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:end-before: step-2
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To try it out, make a 1GB volume called :test'.
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.. only:: libcloud
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.. literalinclude:: ../samples/libcloud/block_storage.py
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:language: python
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:start-after: step-2
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:end-before: step-3
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::
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<StorageVolume id=755ab026-b5f2-4f53-b34a-6d082fb36689 size=1 driver=OpenStack>
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.. only:: shade
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.. literalinclude:: ../samples/shade/block_storage.py
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:language: python
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:start-after: step-2
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:end-before: step-3
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.. note:: The parameter :code:`size` is in gigabytes.
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To see if the volume creation was successful, list all volumes:
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.. only:: libcloud
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.. literalinclude:: ../samples/libcloud/block_storage.py
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:language: python
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:start-after: step-3
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:end-before: step-4
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::
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[<StorageVolume id=755ab026-b5f2-4f53-b34a-6d082fb36689 size=1 driver=OpenStack>]
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.. only:: shade
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.. literalinclude:: ../samples/shade/block_storage.py
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:language: python
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:start-after: step-3
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:end-before: step-4
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Attach the storage volume to a running instance.
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Use Block Storage for the Fractal database server
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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You need a server for the dedicated database. Use the image, flavor, and
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keypair that you used in :doc:`/getting_started` to launch an
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:code:`app-database` instance.
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You also need a security group to permit access to the database server (for
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MySQL, port 3306) from the network:
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.. only:: libcloud
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.. literalinclude:: ../samples/libcloud/block_storage.py
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:language: python
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:start-after: step-4
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:end-before: step-5
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.. only:: shade
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.. literalinclude:: ../samples/shade/block_storage.py
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:language: python
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:start-after: step-4
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:end-before: step-5
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Create a volume object by using the unique identifier (UUID) for the
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volume. Then, use the server object from the previous code snippet to
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attach the volume to it at :code:`/dev/vdb`:
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.. only:: libcloud
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.. literalinclude:: ../samples/libcloud/block_storage.py
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:language: python
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:start-after: step-5
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:end-before: step-6
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.. only:: shade
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.. literalinclude:: ../samples/shade/block_storage.py
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:language: python
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:start-after: step-5
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:end-before: step-6
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Log in to the server to run the following steps.
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.. note:: Replace :code:`IP_SERVICES` with the IP address of the
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services instance and USERNAME to the appropriate user name.
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Now prepare the empty block device.
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::
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$ ssh -i ~/.ssh/id_rsa USERNAME@IP_SERVICES
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# fdisk -l
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# mke2fs /dev/vdb
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# mkdir /mnt/database
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# mount /dev/vdb /mnt/database
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.. todo:: Outputs missing, add attaching log from dmesg.
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Stop the running MySQL database service and move the database files from
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:file:`/var/lib/mysql` to the new volume, which is temporarily mounted at
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:file:`/mnt/database`.
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::
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# systemctl stop mariadb
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# mv /var/lib/mysql/* /mnt/database
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Sync the file systems and mount the block device that contains the database
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files to :file:`/var/lib/mysql`.
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::
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# sync
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# umount /mnt/database
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# rm -rf /mnt/database
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# echo "/dev/vdb /var/lib/mysql ext4 defaults 1 2" >> /etc/fstab
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# mount /var/lib/mysql
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Finally, start the stopped MySQL database service and validate that everything
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works as expected.
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::
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# systemctl start mariadb
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# mysql -ufaafo -ppassword -h localhost faafo -e 'show tables;'
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Extras
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~~~~~~
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You can detach the volume and reattach it elsewhere, or use the following
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steps to delete the volume.
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.. warning::
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The following operations are destructive and result in data loss.
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To detach and delete a volume:
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.. only:: libcloud
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.. literalinclude:: ../samples/libcloud/block_storage.py
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:start-after: step-6
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:end-before: step-7
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::
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True
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.. note:: :code:`detach_volume` and :code:`destroy_volume` take a
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volume object, not a name.
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.. only:: shade
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.. literalinclude:: ../samples/shade/block_storage.py
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:language: python
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:start-after: step-6
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:end-before: step-7
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.. only:: libcloud
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Other features, such as creating volume snapshots, are useful for backups:
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.. literalinclude:: ../samples/libcloud/block_storage.py
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:language: python
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:start-after: step-7
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:end-before: step-8
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.. todo:: Do we need a note here to mention that 'test' is the
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volume name and not the volume object?
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For information about these and other calls, see
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`libcloud documentation <http://ci.apache.org/projects/libcloud/docs/compute/drivers/openstack.html>`_.
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Work with the OpenStack Database service
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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Previously, you manually created the database, which is useful for a a single
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database that you rarely update. However, the OpenStack :code:`trove`
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component provides Database as a Service (DBaaS).
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.. note:: This OpenStack Database service is not installed in many
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clouds right now, but if your cloud supports it, it can
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make your life a lot easier when working with databases.
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SDKs do not generally support the service yet, but you can use the
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'trove' command-line client to work with it instead.
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To install the 'trove' command-line client, see
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`Install the OpenStack command-line clients <http://docs.openstack.org/cli-reference/content/install_clients.html>`_.
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To set up environment variables for your cloud in an :file:`openrc.sh`
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file, see
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`Set environment variables using the OpenStack RC file <http://docs.openstack.org/cli-reference/content/cli_openrc.html>`_.
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Ensure you have an :file:`openrc.sh` file, source it, and validate that
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your trove client works: ::
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$ cat openrc.sh
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export OS_USERNAME=your_auth_username
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export OS_PASSWORD=your_auth_password
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export OS_TENANT_NAME=your_project_name
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export OS_AUTH_URL=http://controller:5000/v2.0
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export OS_REGION_NAME=your_region_name
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$ source openrc.sh
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$ trove --version
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1.0.9
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For information about supported features and how to work with an
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existing database service installation, see
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`Database as a Service in OpenStack <http://www.slideshare.net/hastexo/hands-on-trove-database-as-a-service-in-openstack-33588994>`_.
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Next steps
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~~~~~~~~~~
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You should now be fairly confident working with Block Storage volumes.
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For information about other calls, see the volume documentation for
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your SDK. Or, try one of these tutorial steps:
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* :doc:`/orchestration`: Automatically orchestrate your application.
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* :doc:`/networking`: Learn about complex networking.
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* :doc:`/advice`: Get advice about operations.
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