the node was low on resource ephemeral storage

At the back end level, you can scale capacity by adding more back ends and restarting the service. The Block Storage service can use multiple storage solutions as discrete back ends. Both Block Storage and Object Storage services support Red Hat Ceph as a back end. For example, when using Red Hat Ceph as a Block Storage back end, you can scale storage capacity and redundancy by adding more Ceph OSD (Object Storage Daemon) nodes. In general, a clustered storage solution provides greater back end scalability. The following sections discuss each storage type’s architecture and feature set in detail, within the context of specific storage criteria. Shares are similar to volumes in this regard, except that they can be consumed by multiple instances.

They do not enjoy the same level of access and performance as containers, but they do have a larger feature set and have more native security features than containers. On the other hand, volumes are used primarily for instance consumption. Container usage is geared more towards services.

Containers are designed for wide access, and as such feature the highest throughput, access, and fault tolerance among all storage types. For more information about Technology Preview features, see Scope of Coverage Details.Įach storage type is designed to address specific storage requirements. It should only be used for testing, and should not be deployed in a production environment. The OpenStack Shared File System service is available in this release as a Technology Preview, and therefore is not fully supported by Red Hat. Shares allow tenants within the cloud to openly share storage, and can be consumed by multiple instances simultaneously. Shares The OpenStack Shared File System service ( openstack-manila) provides the means to easily provision remote, shareable file systems, or shares. For example, the Data Processing service ( openstack-sahara) can manage all of its binaries, data input, data output, and templates directly through the Object Storage service. As such, the Object Storage service can be used as a repository by nearly every service within the cloud. While a volume’s contents can only be accessed through instances, the objects inside a container can be accessed through the Object Storage REST API. The Object Storage service organizes these objects through containers. The OpenStack Object Storage service ( openstack-swift) provides a fully-distributed storage solution used to store any kind of static data or binary object, such as media files, large datasets, and disk images. In such cases, the Block Storage service can write images to a volume in turn, the volume can be used as a bootable root volume for an instance. Instances can also be configured to use absolutely no ephemeral storage. For more information about volumes, see Chapter 2, Block Storage and Volumes. In addition, you can also encrypt volumes for added security.

Volumes also provide inherent redundancy and disaster recovery through backups and snapshots. Volumes can be detached and re-attached to instances at will, and can only be accessed through the instance they are attached to. Users can attach volumes to instances in order to augment their ephemeral storage with general-purpose persistent storage. The OpenStack Block Storage service ( openstack-cinder) allows users to access block storage devices through volumes. OpenStack uses the following types of persistent storage: This storage is used for any data that needs to be reused, either by different instances or beyond the life of a specific instance. Persistent storage, on the other hand, is designed to survive ('persist') independent of any running instance. This type of storage is useful for basic runtime requirements, such as storing the instance’s operating system. Once that instance is terminated, so is its ephemeral storage. Ephemeral storage is storage that is associated only to a specific Compute instance. OpenStack recognizes two types of storage: ephemeral and persistent.

The node was low on resource ephemeral storage