Storage
DT Cloud Services Cloud offers three types of storage: ephemeral, block and object. Ephemeral storage is the internal storage of a virtual machine. Block storage are persistent storage devices that can be attached to and moved between different virtual machines, similar to a portable HDD hard disk. Object storage is a flat storage architecture for unstructured data.
Only block storage is managed as an OpenStack service as Cinder volumes, which in Boron has two back-end storage drivers - Ceph and Datera. Table 1 lists some differences between the storage types.
Ephemeral storage | Block storage | Object storage | |
|---|---|---|---|
Usage | Internal storage used for the VM operating system. | Persistent and scalable storage that can be attached to VMs. | Storage architecture used for unstructured data, including images. |
Accessed through | Block device/file system | Block device that can be partitioned, formatted and mounted | REST API |
Accessed from | Within a VM | Within a VM | Anywhere |
Managed by | Nova | Cinder | Swift |
Persistence | Until VM is terminated | Until deleted by user | Until deleted by user |
Sizing and limits | Via flavors | User specification at volume creation time | Limited by the amount of available physical storage |
Table 1. Differences between storage types.
Further information on storage options: