Cinder virtualizes storage enabling VMs to use persistent block storage through Nova. OpenStack consumers should write data that must exist beyond the lifecycle of the guest to Cinder volumes. The volume can be accessed afterwards by a different guest.
Glance provides images to VMs. Generally, the images are block devices containing DVDs or virtual machines. VMs can be booted from these images or have the images attached to them. Glance storage now can use Red Hat Ceph storage, Dell EMC Unity or Dell EMC SC series storage.
Dell EMC Manila driver framework (EMCShareDriver) delivers a shared filesystem in OpenStack. The plugin-based Dell EMC Manila driver design is compatible with various plugins to control Dell EMC storage products.
The Dell EMC Unity plugin manages the Dell EMC Unity Storage System for shared filesystems.
The Dell EMC Unity driver is a REST API. Unity Storage System Manila backends are a one-to-one managed storage system. Each Manila backend configures a Unity Storage System. See https://docs.openstack.org/manila/train/admin/emc_unity_driver.html.
Swift provides an object storage interface to VMs and other OpenStack consumers. Unlike block storage where the guest is provided a block device of a given format and is accessible within the cluster, object storage is not provided through the guest. Object storage is generally implemented as a HTTP/HTTPS-based service through a web server. Client implementations within the guest or external OpenStack clients would interact with Swift without any configuration required of the guest other than providing the requisite network access. For example, a VM within OpenStack can put data into Swift, and later external clients could pull that data for additional processing.
As with other OpenStack services, there are client and server components for each storage service. The server component can be modified to use a particular type of storage rather than the default. For example, Cinder uses local disks as the storage back-end by default. The Dell EMC Ready Architecture for Red Hat OpenStack Platform modifies the default configuration for these services.
All virtual machines will need a virtual drive that is used for the OS. Two options are available:
- Ephemeral disks
- Boot from volume or snapshot, hosted on Red Hat Ceph storage, Dell EMC Unity storage or SC series storage arrays.
Ephemeral disks are virtual drives that are created when a VM is created, and destroyed when the VM is removed. The virtual drives can be stored on the local drives of the Nova host or on a shared file system, such as Ceph Rados Block Device (RBD). During the planning process, decisions can be made to place ephemeral on local or shared storage, it is recommended that a shared backend is used which will allow live migration.
Boot from volume/snapshot will use one of the Cinder backends.
The Dell EMC Ready Architecture for Red Hat OpenStack Platform includes alternate implementations of Cinder that enable the cluster to fit many needs. Cinder has been validated using each of the back-ends independently, and multi back-ends utilizing multiple Storage back-ends consisting of two or all of: