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


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


Accessed from

Within a VM

Within a VM


Managed by





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:

Block storage

Object storage

Local storage