To use the Block Storage API effectively, you should understand several key concepts:
A volume is a detachable block storage device. You can think of it as a USB hard drive. It can only be attached to one instance at a time.
The volume type is the type of a block storage volume. You may define whatever types work best for you, such as SATA, SCSCI, SSD, etc. These can be customized or defined by the OpenStack admin.
You may also define extra_specs associated with your volume types. For instance, you could have a VolumeType=SATA, with extra_specs (RPM=10000, RAID-Level=5) . Extra_specs are defined and customized by the admin.
