Manila Administrators create share group types with shared_file_systems_share_types and group-specs to
allow users to request a group type of share group to create. The
Administrator chooses a name for the share group type and decides how to
communicate the significance of the different share group types in terms
that the users should understand or need to know. By design, most of the
details of a share group type (the extra-specs) are not exposed to users
— only Administrators.

Share group Types

Refer to the manila client command-line help for information on how
to create a share group type and set “share types”, “group-spec”
key/value pairs for a share group type.

Group-Specs

The group specs contains the group capabilities, similar to
snapshot_support in share types. Users know what a group can do from
group specs.

The group specs is an exact match requirement in share group filter
(such as ConsistentSnapshotFilter). When the ConsistentSnapshotFilter is
enabled (it is enabled by default), the scheduler will only create a
share group on a backend that reports capabilities that match the share
group type’s group-spec keys.

Common Group Capabilities

For group capabilities that apply to multiple backends a common
capability can be created. Like all other backend reported group
capabilities, these group capabilities can be used verbatim as
group_specs in share group types used to create share groups.

• consistent_snapshot_support –
  indicates that a backend can enable you to create snapshots at the exact
  same point in time from multiple shares. The default value of the
  consistent_snapshot_support capability (if a driver doesn’t report it)
  is None. Administrators can make a share group type use consistent
  snapshot support by setting this group-spec to ‘host’.