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Chapter 3. Object Storage service
OpenStack Object Storage (swift) stores its objects (data) in containers, which are similar to directories in a file system although they cannot be nested. Containers provide an easy way for users to store any kind of unstructured data. For example, objects might include photos, text files, or images. Stored objects are not compressed.
3.1. Object Storage rings
Object Storage uses a data structure called the Ring to distribute partition space across the cluster. This partition space is core to the data durability engine in the Object Storage service. It allows the Object Storage service to quickly and easily synchronize each partition across the cluster.
Rings contain information about Object Storage partitions and how partitions are distributed among the different nodes and disks. When any Object Storage component interacts with data, a quick lookup is performed locally in the ring to determine the possible partitions for each object.
The Object Storage service has three rings to store different types of data: one for account information, another for containers (to facilitate organizing objects under an account), and another for object replicas.
3.1.1. Rebalancing rings
When you change the Object Storage environment by adding or removing storage capacity, nodes, or disks, you must rebalance the rings. You can run openstack overcloud deploy to rebalance the rings, but this method redeploys the entire overcloud. This can be cumbersome, especially if you have a large overcloud. Alternatively, run the following command on the undercloud to rebalance the rings:
source ~/stackrc ansible-playbook -i /usr/bin/tripleo-ansible-inventory /usr/share/openstack-tripleo-common/playbooks/swift_ring_rebalance.yaml
source ~/stackrc
ansible-playbook -i /usr/bin/tripleo-ansible-inventory
/usr/share/openstack-tripleo-common/playbooks/swift_ring_rebalance.yaml3.1.2. Checking cluster health
The Object Storage service runs many processes in the background to ensure long-term data availability, durability, and persistence. For example:
- Auditors constantly re-read database and object files and compare them using checksums to make sure there is no silent bit-rot. Any database or object file that no longer matches its checksum is quarantined and becomes unreadable on that node. The replicators then copy one of the other replicas to make the local copy available again.
- Objects and files can disappear when you replace disks or nodes or when objects are quarantined. When this happens, replicators copy missing objects or database files to one of the other nodes.
The Object Storage service includes a tool called swift-recon that collects data from all nodes and checks the overall cluster health.
To use swift-recon, log in to one of the controller nodes and run the following command:
As an alternative, use the --all option to return additional output.
This command queries all servers on the ring for the following data:
- Async pendings: If the cluster load is too high and processes can’t update database files fast enough, some updates will occur asynchronously. These numbers should decrease over time.
- Replication metrics: Notice the replication timestamps; full replication passes should happen frequently and there should be few errors. An old entry, (for example, an entry with a timestamp from six months ago) indicates that replication on the node has not completed in the last six months.
- Ring md5sums: This ensures that all ring files are consistent on all nodes.
-
swift.confmd5sums: This ensures that all ring files are consistent on all nodes. - Quarantined files: There should be no (or very few) quarantined files for all nodes.
- Time-sync: All nodes must be synchronized.
3.1.3. Increasing ring partition power
The ring power determines the partition to which a resource (account, container, or object) is mapped. The partition is included in the path under which the resource is stored in a back end filesystem. Therefore, changing the partition power requires relocating resources to new paths in the back end filesystems.
In a heavily populated cluster, a relocation process is time-consuming. To avoid downtime, relocate resources while the cluster is still operating. You must do this without temporarily losing access to data or compromising the performance of processes, such as replication and auditing. For assistance with increasing ring partition power, contact Red Hat support.
3.1.4. Creating custom rings
As technology advances and demands for storage capacity increase, creating custom rings is a way to update existing Object Storage clusters.
When you add new nodes to a cluster, their characteristics may differ from those of the original nodes. Without custom adjustments, the larger capacity of the new nodes may be underutilized. Or, if weights change in the rings, data dispersion can become uneven, which reduces safety.
Automation may not keep pace with future technology trends. For example, some older Object Storage clusters in use today originated before SSDs were available.
The ring builder helps manage Object Storage as clusters grow and technologies evolve. For assistance with creating custom rings, contact Red Hat support.
3.2. Object Storage service administration
The following procedures explain how to customize the Object Storage service.
3.2.1. Configuring fast-post
By default, the Object Storage service copies an object whole whenever any part of its metadata changes. You can prevent this by using the fast-post feature. The fast-post feature saves time when you change the content types of multiple large objects.
To enable the fast-post feature, disable the object_post_as_copy option on the Object Storage proxy service by doing the following:
Edit
swift_params.yaml:cat > swift_params.yaml << EOF parameter_defaults: ExtraConfig: swift::proxy::copy::object_post_as_copy: False EOFcat > swift_params.yaml << EOF parameter_defaults: ExtraConfig: swift::proxy::copy::object_post_as_copy: False EOFCopy to Clipboard Copied! Toggle word wrap Toggle overflow Include the parameter file when you deploy or update the overcloud:
openstack overcloud deploy [... previous args ...] -e swift_params.yaml
openstack overcloud deploy [... previous args ...] -e swift_params.yamlCopy to Clipboard Copied! Toggle word wrap Toggle overflow
3.2.2. Enabling at-rest encryption
By default, objects uploaded to Object Storage are kept unencrypted. Because of this, it is possible to access objects directly from the file system. This can present a security risk if disks are not properly erased before they are discarded.
You can use OpenStack Key Manager (barbican) to encrypt at-rest swift objects. For more information, see Encrypt at-rest swift objects.
3.2.3. Deploying a standalone Object Storage cluster
You can use the composable role concept to deploy a standalone Object Storage (openstack-swift) cluster with the bare minimum of additional services (for example Keystone, HAProxy). The Creating a roles_data File section has information on roles.
3.2.3.1. Creating the roles_data.yaml File
-
Copy the
roles_data.yamlfrom/usr/share/openstack-tripleo-heat-templates. - Edit the new file.
- Remove unneeded controller roles, for example Aodh*, Ceilometer*, Ceph*, Cinder*, Glance*, Heat*, Ironic*, Manila*, Mistral*, Nova*, Octavia*, Swift*.
-
Locate the ObjectStorage role within
roles_data.yaml. -
Copy this role to a new role within that same file and name it
ObjectProxy. -
Replace
SwiftStoragewithSwiftProxyin this role.
The example roles_data.yaml file below shows sample roles.
3.2.3.2. Deploying the New Roles
Deploy the overcloud with your regular openstack deploy command, including the new roles.
openstack overcloud deploy --templates -r roles_data.yaml -e [...]
openstack overcloud deploy --templates -r roles_data.yaml -e [...]3.3. Basic container management
To help with organization, pseudo-folders are logical devices that can contain objects (and can be nested). For example, you might create an Images folder in which to store pictures and a Media folder in which to store videos.
You can create one or more containers in each project, and one or more objects or pseudo-folders in each container.
3.3.1. Creating a container
- In the dashboard, select Project > Object Store > Containers.
- Click Create Container.
Specify the Container Name, and select one of the following in the Container Access field.
Expand Type Description PrivateLimits access to a user in the current project.
PublicPermits API access to anyone with the public URL. However, in the dashboard, project users cannot see public containers and data from other projects.
- Click Create Container.
New containers use the default storage policy. If you have multiple storage policies defined (for example, a default and another that enables erasure coding), you can configure a container to use a non-default storage policy through the command line. To do so, run:
swift post -H "X-Storage-Policy:POLICY" CONTAINERNAME
# swift post -H "X-Storage-Policy:POLICY" CONTAINERNAMEWhere:
- POLICY is the name or alias of the policy you want the container to use.
- CONTAINERNAME is the name of the container.
3.3.2. Creating a pseudo folder for a container
- In the dashboard, select Project > Object Store > Containers.
- Click the name of the container to which you want to add the pseudo-folder.
- Click Create Pseudo-folder.
- Specify the name in the Pseudo-folder Name field, and click Create.
3.3.3. Deleting a container
- In the dashboard, select Project > Object Store > Containers.
- Browse for the container in the Containers section, and ensure all objects have been deleted (see Section 3.3.6, “Deleting an object”).
- Select Delete Container in the container’s arrow menu.
- Click Delete Container to confirm the container’s removal.
3.3.4. Uploading an object
If you do not upload an actual file, the object is still created (as placeholder) and can later be used to upload the file.
- In the dashboard, select Project > Object Store > Containers.
- Click the name of the container in which the uploaded object will be placed; if a pseudo-folder already exists in the container, you can click its name.
- Browse for your file, and click Upload Object.
Specify a name in the Object Name field:
- Pseudo-folders can be specified in the name using a / character (for example, Images/myImage.jpg). If the specified folder does not already exist, it is created when the object is uploaded.
- A name that is not unique to the location (that is, the object already exists) overwrites the object’s contents.
- Click Upload Object.
3.3.5. Copying an object
- In the dashboard, select Project > Object Store > Containers.
- Click the name of the object’s container or folder (to display the object).
- Click Upload Object.
- Browse for the file to be copied, and select Copy in its arrow menu.
Specify the following:
Expand Field Description Destination container
Target container for the new object.
Path
Pseudo-folder in the destination container; if the folder does not already exist, it is created.
Destination object name
New object’s name. If you use a name that is not unique to the location (that is, the object already exists), it overwrites the object’s previous contents.
- Click Copy Object.
3.3.6. Deleting an object
- In the dashboard, select Project > Object Store > Containers.
- Browse for the object, and select Delete Object in its arrow menu.
- Click Delete Object to confirm the object’s removal.
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