Scope of this document

This page describes how to enable multiple stores in glance.

Prerequisites

• Glance version 17.0.0 or Later
• Glance Store Library 0.25.0 or Later
• Glance not using the Glance Registry
• Available backends

Procedure

In this section, we discuss what configuration options are available
to operators to enable multiple stores support.

• in the [DEFAULT] options group:

  • enabled_backends must be set as a key:value pair
    where key represents the identifier for the store and value will be the
    type of the store. Valid values are one of file,
    http, rbd, swift,
    cinder or vmware. In order to have multiple
    stores operator can specify multiple key:value separated by comma.

    Warning

    The store identifier prefix os_glance_ is reserved. If
    you define a store identifier with this prefix, the glance service will
    refuse to start.

    The http store type is always treated by Glance as a read-only store.
    This is indicated in the response to the /v2/stores/info
    call, where an http type store will have the attribute
    read-only: True in addition to the usual id
    and description fields.

    [DEFAULT]
    enabled_backends = fast:rbd, cheap:rbd, shared:file, reliable:file

• in the [glance_store] options group:

  • default_backend must be set to one of the identifier
    which are defined using enabled_backends option. If
    default_backend is not set or if it is not representing one
    of the valid store drivers then it will prevent glance api service from
    starting.

    [glance_store]
    default_backend = fast

• For each of the store identifier defined in
  enabled_backends section operator needs to add a new config
  group which will define config options related to that particular
  store.

  [shared]
  filesystem_store_datadir = /opt/stack/data/glance/shared_images/
  store_description = "Shared filesystem store"
  
  [reliable]
  filesystem_store_datadir = /opt/stack/data/glance/reliable
  store_description = "Reliable filesystem backend"
  
  [fast]
  store_description = "Fast rbd backend"
  rbd_store_chunk_size = 8
  rbd_store_pool = images
  rbd_store_user = admin
  rbd_store_ceph_conf = /etc/ceph/ceph.conf
  rados_connect_timeout = 0
  
  [cheap]
  store_description = "Cheap rbd backend"
  rbd_store_chunk_size = 8
  rbd_store_pool = images
  rbd_store_user = admin
  rbd_store_ceph_conf = /etc/ceph/ceph1.conf
  rados_connect_timeout = 0

Store Configuration Issues

Please keep the following points in mind.

• Due to the special read only nature and characteristics of the http
  store type, configuring multiple instances of the http type store
  is not supported. (This constraint is not currently
  enforced in the code.)
• Each instance of the filesystem store must have a
  different value for the filesystem_store_datadir. (This
  constraint is not currently enforced in the code.)

Reserved Stores

With the Train release, Glance is beginning a transition from its
former reliance upon local directories for temporary data storage to the
ability to use backend stores accessed via the glance_store library.

In the Train release, the use of backend stores for this purpose is
optional unless you are using the multi store support
feature. Since you are reading this document, this situation
most likely applies to you.

The reserved stores are not intended to be exposed to end users. Thus
they will not appear in the response to the store discovery call, GET
/v2/info/stores, or as values in the
OpenStack-image-store-ids response header of the
image-create call.

You do not get to select the name of a reserved store; these are
defined by Glance and begin with the prefix os_glance_. In
the Train release, you do not get to select the store type: all reserved
stores must be of type filesystem.

Currently, there are two reserved stores:

os_glance_tasks_store

This store is used for the tasks engine. It replaces the use of the
DEPRECATED configuration option [task]/work_dir.

os_glance_staging_store

This store is used for the staging area for the interoperable image
import process. It replaces the use of the DEPRECATED configuration
option [DEFAULT]/node_staging_uri.

Configuration

As mentioned above, you do not get to select the name or the type of
a reserved store (though we anticipate that you will be able configure
the store type in a future release).

The reserved stores must be of type filesystem. Hence, you
must provide configuration for them in your glance-api.conf
file. You do this by introducing a section in
glance-api.conf for each reserved store as follows:

[os_glance_tasks_store]
filesystem_store_datadir = /var/lib/glance/tasks_work_dir

[os_glance_staging_store]
filesystem_store_datadir = /var/lib/glance/staging

Since these are both filesystem stores (remember, you do not get a
choice) the only option you must configure for each is the
filesystem_store_datadir. Please keep the following points
in mind:

• The path for filesystem_store_datadir used for the
  reserved stores must be different from the path you are
  using for any filesystem store you have listed in
  enabled_backends. Using the same data directory for
  multiple filesystem stores is unsupported and may lead
  to data loss.
• The identifiers for reserved stores, that is,
  os_glance_tasks_store and
  os_glance_staging_store, must not be
  included in the enabled_backends list.
• The reserved stores will not appear in the store
  discovery response or as values in the
  OpenStack-image-store-ids response header of the
  image-create call.
• The reserved stores will not be accepted as the
  value of the X-Image-Meta-Store header on the
  image-data-upload call or the image-import call.